1. 24 2月, 2013 40 次提交
    • H
      ksm: enable KSM page migration · b79bc0a0
      Hugh Dickins 提交于
      Migration of KSM pages is now safe: remove the PageKsm restrictions from
      mempolicy.c and migrate.c.
      
      But keep PageKsm out of __unmap_and_move()'s anon_vma contortions, which
      are irrelevant to KSM: it looks as if that code was preventing hotremove
      migration of KSM pages, unless they happened to be in swapcache.
      
      There is some question as to whether enforcing a NUMA mempolicy migration
      ought to migrate KSM pages, mapped into entirely unrelated processes; but
      moving page_mapcount > 1 is only permitted with MPOL_MF_MOVE_ALL anyway,
      and it seems reasonable to assume that you wouldn't set MADV_MERGEABLE on
      any area where this is a worry.
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Petr Holasek <pholasek@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Izik Eidus <izik.eidus@ravellosystems.com>
      Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b79bc0a0
    • H
      ksm: make !merge_across_nodes migration safe · 4146d2d6
      Hugh Dickins 提交于
      The new KSM NUMA merge_across_nodes knob introduces a problem, when it's
      set to non-default 0: if a KSM page is migrated to a different NUMA node,
      how do we migrate its stable node to the right tree?  And what if that
      collides with an existing stable node?
      
      ksm_migrate_page() can do no more than it's already doing, updating
      stable_node->kpfn: the stable tree itself cannot be manipulated without
      holding ksm_thread_mutex.  So accept that a stable tree may temporarily
      indicate a page belonging to the wrong NUMA node, leave updating until the
      next pass of ksmd, just be careful not to merge other pages on to a
      misplaced page.  Note nid of holding tree in stable_node, and recognize
      that it will not always match nid of kpfn.
      
      A misplaced KSM page is discovered, either when ksm_do_scan() next comes
      around to one of its rmap_items (we now have to go to cmp_and_merge_page
      even on pages in a stable tree), or when stable_tree_search() arrives at a
      matching node for another page, and this node page is found misplaced.
      
      In each case, move the misplaced stable_node to a list of migrate_nodes
      (and use the address of migrate_nodes as magic by which to identify them):
      we don't need them in a tree.  If stable_tree_search() finds no match for
      a page, but it's currently exiled to this list, then slot its stable_node
      right there into the tree, bringing all of its mappings with it; otherwise
      they get migrated one by one to the original page of the colliding node.
      stable_tree_search() is now modelled more like stable_tree_insert(), in
      order to handle these insertions of migrated nodes.
      
      remove_node_from_stable_tree(), remove_all_stable_nodes() and
      ksm_check_stable_tree() have to handle the migrate_nodes list as well as
      the stable tree itself.  Less obviously, we do need to prune the list of
      stale entries from time to time (scan_get_next_rmap_item() does it once
      each full scan): whereas stale nodes in the stable tree get naturally
      pruned as searches try to brush past them, these migrate_nodes may get
      forgotten and accumulate.
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Petr Holasek <pholasek@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Izik Eidus <izik.eidus@ravellosystems.com>
      Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      4146d2d6
    • H
      ksm: make KSM page migration possible · c8d6553b
      Hugh Dickins 提交于
      KSM page migration is already supported in the case of memory hotremove,
      which takes the ksm_thread_mutex across all its migrations to keep life
      simple.
      
      But the new KSM NUMA merge_across_nodes knob introduces a problem, when
      it's set to non-default 0: if a KSM page is migrated to a different NUMA
      node, how do we migrate its stable node to the right tree?  And what if
      that collides with an existing stable node?
      
      So far there's no provision for that, and this patch does not attempt to
      deal with it either.  But how will I test a solution, when I don't know
      how to hotremove memory?  The best answer is to enable KSM page migration
      in all cases now, and test more common cases.  With THP and compaction
      added since KSM came in, page migration is now mainstream, and it's a
      shame that a KSM page can frustrate freeing a page block.
      
      Without worrying about merge_across_nodes 0 for now, this patch gets KSM
      page migration working reliably for default merge_across_nodes 1 (but
      leave the patch enabling it until near the end of the series).
      
      It's much simpler than I'd originally imagined, and does not require an
      additional tier of locking: page migration relies on the page lock, KSM
      page reclaim relies on the page lock, the page lock is enough for KSM page
      migration too.
      
      Almost all the care has to be in get_ksm_page(): that's the function which
      worries about when a stable node is stale and should be freed, now it also
      has to worry about the KSM page being migrated.
      
      The only new overhead is an additional put/get/lock/unlock_page when
      stable_tree_search() arrives at a matching node: to make sure migration
      respects the raised page count, and so does not migrate the page while
      we're busy with it here.  That's probably avoidable, either by changing
      internal interfaces from using kpage to stable_node, or by moving the
      ksm_migrate_page() callsite into a page_freeze_refs() section (even if not
      swapcache); but this works well, I've no urge to pull it apart now.
      
      (Descents of the stable tree may pass through nodes whose KSM pages are
      under migration: being unlocked, the raised page count does not prevent
      that, nor need it: it's safe to memcmp against either old or new page.)
      
      You might worry about mremap, and whether page migration's rmap_walk to
      remove migration entries will find all the KSM locations where it inserted
      earlier: that should already be handled, by the satisfyingly heavy hammer
      of move_vma()'s call to ksm_madvise(,,,MADV_UNMERGEABLE,).
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Petr Holasek <pholasek@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Izik Eidus <izik.eidus@ravellosystems.com>
      Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      c8d6553b
    • H
      ksm: remove old stable nodes more thoroughly · cbf86cfe
      Hugh Dickins 提交于
      Switching merge_across_nodes after running KSM is liable to oops on stale
      nodes still left over from the previous stable tree.  It's not something
      that people will often want to do, but it would be lame to demand a reboot
      when they're trying to determine which merge_across_nodes setting is best.
      
      How can this happen?  We only permit switching merge_across_nodes when
      pages_shared is 0, and usually set run 2 to force that beforehand, which
      ought to unmerge everything: yet oopses still occur when you then run 1.
      
      Three causes:
      
      1. The old stable tree (built according to the inverse
         merge_across_nodes) has not been fully torn down.  A stable node
         lingers until get_ksm_page() notices that the page it references no
         longer references it: but the page is not necessarily freed as soon as
         expected, particularly when swapcache.
      
         Fix this with a pass through the old stable tree, applying
         get_ksm_page() to each of the remaining nodes (most found stale and
         removed immediately), with forced removal of any left over.  Unless the
         page is still mapped: I've not seen that case, it shouldn't occur, but
         better to WARN_ON_ONCE and EBUSY than BUG.
      
      2. __ksm_enter() has a nice little optimization, to insert the new mm
         just behind ksmd's cursor, so there's a full pass for it to stabilize
         (or be removed) before ksmd addresses it.  Nice when ksmd is running,
         but not so nice when we're trying to unmerge all mms: we were missing
         those mms forked and inserted behind the unmerge cursor.  Easily fixed
         by inserting at the end when KSM_RUN_UNMERGE.
      
      3.  It is possible for a KSM page to be faulted back from swapcache
         into an mm, just after unmerge_and_remove_all_rmap_items() scanned past
         it.  Fix this by copying on fault when KSM_RUN_UNMERGE: but that is
         private to ksm.c, so dissolve the distinction between
         ksm_might_need_to_copy() and ksm_does_need_to_copy(), doing it all in
         the one call into ksm.c.
      
      A long outstanding, unrelated bugfix sneaks in with that third fix:
      ksm_does_need_to_copy() would copy from a !PageUptodate page (implying I/O
      error when read in from swap) to a page which it then marks Uptodate.  Fix
      this case by not copying, letting do_swap_page() discover the error.
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Petr Holasek <pholasek@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Izik Eidus <izik.eidus@ravellosystems.com>
      Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Acked-by: NMel Gorman <mgorman@suse.de>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      cbf86cfe
    • H
      ksm: get_ksm_page locked · 8aafa6a4
      Hugh Dickins 提交于
      In some places where get_ksm_page() is used, we need the page to be locked.
      
      When KSM migration is fully enabled, we shall want that to make sure that
      the page just acquired cannot be migrated beneath us (raised page count is
      only effective when there is serialization to make sure migration
      notices).  Whereas when navigating through the stable tree, we certainly
      do not want to lock each node (raised page count is enough to guarantee
      the memcmps, even if page is migrated to another node).
      
      Since we're about to add another use case, add the locked argument to
      get_ksm_page() now.
      
      Hmm, what's that rcu_read_lock() about?  Complete misunderstanding, I
      really got the wrong end of the stick on that!  There's a configuration in
      which page_cache_get_speculative() can do something cheaper than
      get_page_unless_zero(), relying on its caller's rcu_read_lock() to have
      disabled preemption for it.  There's no need for rcu_read_lock() around
      get_page_unless_zero() (and mapping checks) here.  Cut out that silliness
      before making this any harder to understand.
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Petr Holasek <pholasek@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Izik Eidus <izik.eidus@ravellosystems.com>
      Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      8aafa6a4
    • H
      ksm: reorganize ksm_check_stable_tree · ee0ea59c
      Hugh Dickins 提交于
      Memory hotremove's ksm_check_stable_tree() is pitifully inefficient
      (restarting whenever it finds a stale node to remove), but rearrange so
      that at least it does not needlessly restart from nid 0 each time.  And
      add a couple of comments: here is why we keep pfn instead of page.
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Petr Holasek <pholasek@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Izik Eidus <izik.eidus@ravellosystems.com>
      Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      ee0ea59c
    • H
      ksm: trivial tidyups · e850dcf5
      Hugh Dickins 提交于
      Add NUMA() and DO_NUMA() macros to minimize blight of #ifdef
      CONFIG_NUMAs (but indeed we don't want to expand struct rmap_item by nid
      when not NUMA).  Add comment, remove "unsigned" from rmap_item->nid, as
      "int nid" elsewhere.  Define ksm_merge_across_nodes 1U when #ifndef NUMA
      to help optimizing out.  Use ?: in get_kpfn_nid().  Adjust a few
      comments noticed in ongoing work.
      
      Leave stable_tree_insert()'s rb_linkage until after the node has been
      set up, as unstable_tree_search_insert() does: ksm_thread_mutex and page
      lock make either way safe, but we're going to copy and I prefer this
      precedent.
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Petr Holasek <pholasek@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Izik Eidus <izik.eidus@ravellosystems.com>
      Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e850dcf5
    • P
      ksm: add sysfs ABI Documentation · f00dc0ee
      Petr Holasek 提交于
      Add sysfs documentation for Kernel Samepage Merging (KSM) including new
      merge_across_nodes knob.
      Signed-off-by: NPetr Holasek <pholasek@redhat.com>
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Izik Eidus <izik.eidus@ravellosystems.com>
      Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      f00dc0ee
    • P
      ksm: allow trees per NUMA node · 90bd6fd3
      Petr Holasek 提交于
      Here's a KSM series, based on mmotm 2013-01-23-17-04: starting with
      Petr's v7 "KSM: numa awareness sysfs knob"; then fixing the two issues
      we had with that, fully enabling KSM page migration on the way.
      
      (A different kind of KSM/NUMA issue which I've certainly not begun to
      address here: when KSM pages are unmerged, there's usually no sense in
      preferring to allocate the new pages local to the caller's node.)
      
      This patch:
      
      Introduces new sysfs boolean knob /sys/kernel/mm/ksm/merge_across_nodes
      which control merging pages across different numa nodes.  When it is set
      to zero only pages from the same node are merged, otherwise pages from
      all nodes can be merged together (default behavior).
      
      Typical use-case could be a lot of KVM guests on NUMA machine and cpus
      from more distant nodes would have significant increase of access
      latency to the merged ksm page.  Sysfs knob was choosen for higher
      variability when some users still prefers higher amount of saved
      physical memory regardless of access latency.
      
      Every numa node has its own stable & unstable trees because of faster
      searching and inserting.  Changing of merge_across_nodes value is
      possible only when there are not any ksm shared pages in system.
      
      I've tested this patch on numa machines with 2, 4 and 8 nodes and
      measured speed of memory access inside of KVM guests with memory pinned
      to one of nodes with this benchmark:
      
        http://pholasek.fedorapeople.org/alloc_pg.c
      
      Population standard deviations of access times in percentage of average
      were following:
      
      merge_across_nodes=1
      2 nodes 1.4%
      4 nodes 1.6%
      8 nodes	1.7%
      
      merge_across_nodes=0
      2 nodes	1%
      4 nodes	0.32%
      8 nodes	0.018%
      
      RFC: https://lkml.org/lkml/2011/11/30/91
      v1: https://lkml.org/lkml/2012/1/23/46
      v2: https://lkml.org/lkml/2012/6/29/105
      v3: https://lkml.org/lkml/2012/9/14/550
      v4: https://lkml.org/lkml/2012/9/23/137
      v5: https://lkml.org/lkml/2012/12/10/540
      v6: https://lkml.org/lkml/2012/12/23/154
      v7: https://lkml.org/lkml/2012/12/27/225
      
      Hugh notes that this patch brings two problems, whose solution needs
      further support in mm/ksm.c, which follows in subsequent patches:
      
      1) switching merge_across_nodes after running KSM is liable to oops
         on stale nodes still left over from the previous stable tree;
      
      2) memory hotremove may migrate KSM pages, but there is no provision
         here for !merge_across_nodes to migrate nodes to the proper tree.
      Signed-off-by: NPetr Holasek <pholasek@redhat.com>
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Acked-by: NRik van Riel <riel@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Izik Eidus <izik.eidus@ravellosystems.com>
      Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      90bd6fd3
    • M
      mm: rename page struct field helpers · 22b751c3
      Mel Gorman 提交于
      The function names page_xchg_last_nid(), page_last_nid() and
      reset_page_last_nid() were judged to be inconsistent so rename them to a
      struct_field_op style pattern.  As it looked jarring to have
      reset_page_mapcount() and page_nid_reset_last() beside each other in
      memmap_init_zone(), this patch also renames reset_page_mapcount() to
      page_mapcount_reset().  There are others like init_page_count() but as
      it is used throughout the arch code a rename would likely cause more
      conflicts than it is worth.
      
      [akpm@linux-foundation.org: fix zcache]
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Suggested-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      22b751c3
    • G
      memcg: avoid dangling reference count in creation failure. · e4715f01
      Glauber Costa 提交于
      When use_hierarchy is enabled, we acquire an extra reference count in
      our parent during cgroup creation.  We don't release it, though, if any
      failure exist in the creation process.
      Signed-off-by: NGlauber Costa <glommer@parallels.com>
      Reported-by: NMichal Hocko <mhocko@suse.cz>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e4715f01
    • G
      memcg: increment static branch right after limit set · 692e89ab
      Glauber Costa 提交于
      We were deferring the kmemcg static branch increment to a later time,
      due to a nasty dependency between the cpu_hotplug lock, taken by the
      jump label update, and the cgroup_lock.
      
      Now we no longer take the cgroup lock, and we can save ourselves the
      trouble.
      Signed-off-by: NGlauber Costa <glommer@parallels.com>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      692e89ab
    • G
      memcg: replace cgroup_lock with memcg specific memcg_lock · 0999821b
      Glauber Costa 提交于
      After the preparation work done in earlier patches, the cgroup_lock can
      be trivially replaced with a memcg-specific lock.  This is an automatic
      translation at every site where the values involved were queried.
      
      The sites where values are written, however, used to be naturally called
      under cgroup_lock.  This is the case for instance in the css_online
      callback.  For those, we now need to explicitly add the memcg lock.
      
      With this, all the calls to cgroup_lock outside cgroup core are gone.
      Signed-off-by: NGlauber Costa <glommer@parallels.com>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      0999821b
    • G
      memcg: fast hierarchy-aware child test · b5f99b53
      Glauber Costa 提交于
      Currently, we use cgroups' provided list of children to verify if it is
      safe to proceed with any value change that is dependent on the cgroup
      being empty.
      
      This is less than ideal, because it enforces a dependency over cgroup
      core that we would be better off without.  The solution proposed here is
      to iterate over the child cgroups and if any is found that is already
      online, we bounce and return: we don't really care how many children we
      have, only if we have any.
      
      This is also made to be hierarchy aware.  IOW, cgroups with hierarchy
      disabled, while they still exist, will be considered for the purpose of
      this interface as having no children.
      
      [akpm@linux-foundation.org: tweak comments]
      Signed-off-by: NGlauber Costa <glommer@parallels.com>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b5f99b53
    • G
      memcg: split part of memcg creation to css_online · d142e3e6
      Glauber Costa 提交于
      This patch is a preparatory work for later locking rework to get rid of
      big cgroup lock from memory controller code.
      
      The memory controller uses some tunables to adjust its operation.  Those
      tunables are inherited from parent to children upon children
      intialization.  For most of them, the value cannot be changed after the
      parent has a new children.
      
      cgroup core splits initialization in two phases: css_alloc and css_online.
      After css_alloc, the memory allocation and basic initialization are done.
      But the new group is not yet visible anywhere, not even for cgroup core
      code.  It is only somewhere between css_alloc and css_online that it is
      inserted into the internal children lists.  Copying tunable values in
      css_alloc will lead to inconsistent values: the children will copy the old
      parent values, that can change between the copy and the moment in which
      the groups is linked to any data structure that can indicate the presence
      of children.
      Signed-off-by: NGlauber Costa <glommer@parallels.com>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d142e3e6
    • G
      memcg: prevent changes to move_charge_at_immigrate during task attach · ee5e8472
      Glauber Costa 提交于
      In memcg, we use the cgroup_lock basically to synchronize against
      attaching new children to a cgroup.  We do this because we rely on
      cgroup core to provide us with this information.
      
      We need to guarantee that upon child creation, our tunables are
      consistent.  For those, the calls to cgroup_lock() all live in handlers
      like mem_cgroup_hierarchy_write(), where we change a tunable in the
      group that is hierarchy-related.  For instance, the use_hierarchy flag
      cannot be changed if the cgroup already have children.
      
      Furthermore, those values are propagated from the parent to the child
      when a new child is created.  So if we don't lock like this, we can end
      up with the following situation:
      
      A                                   B
       memcg_css_alloc()                       mem_cgroup_hierarchy_write()
       copy use hierarchy from parent          change use hierarchy in parent
       finish creation.
      
      This is mainly because during create, we are still not fully connected
      to the css tree.  So all iterators and the such that we could use, will
      fail to show that the group has children.
      
      My observation is that all of creation can proceed in parallel with
      those tasks, except value assignment.  So what this patch series does is
      to first move all value assignment that is dependent on parent values
      from css_alloc to css_online, where the iterators all work, and then we
      lock only the value assignment.  This will guarantee that parent and
      children always have consistent values.  Together with an online test,
      that can be derived from the observation that the refcount of an online
      memcg can be made to be always positive, we should be able to
      synchronize our side without the cgroup lock.
      
      This patch:
      
      Currently, we rely on the cgroup_lock() to prevent changes to
      move_charge_at_immigrate during task migration.  However, this is only
      needed because the current strategy keeps checking this value throughout
      the whole process.  Since all we need is serialization, one needs only
      to guarantee that whatever decision we made in the beginning of a
      specific migration is respected throughout the process.
      
      We can achieve this by just saving it in mc.  By doing this, no kind of
      locking is needed.
      Signed-off-by: NGlauber Costa <glommer@parallels.com>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      ee5e8472
    • G
      memcg: reduce the size of struct memcg 244-fold. · 45cf7ebd
      Glauber Costa 提交于
      In order to maintain all the memcg bookkeeping, we need per-node
      descriptors, which will in turn contain a per-zone descriptor.
      
      Because we want to statically allocate those, this array ends up being
      very big.  Part of the reason is that we allocate something large enough
      to hold MAX_NUMNODES, the compile time constant that holds the maximum
      number of nodes we would ever consider.
      
      However, we can do better in some cases if the firmware help us.  This
      is true for modern x86 machines; coincidentally one of the architectures
      in which MAX_NUMNODES tends to be very big.
      
      By using the firmware-provided maximum number of nodes instead of
      MAX_NUMNODES, we can reduce the memory footprint of struct memcg
      considerably.  In the extreme case in which we have only one node, this
      reduces the size of the structure from ~ 64k to ~2k.  This is
      particularly important because it means that we will no longer resort to
      the vmalloc area for the struct memcg on defconfigs.  We also have
      enough room for an extra node and still be outside vmalloc.
      
      One also has to keep in mind that with the industry's ability to fit
      more processors in a die as fast as the FED prints money, a nodes = 2
      configuration is already respectably big.
      
      [akpm@linux-foundation.org: add check for invalid nid, remove inline]
      Signed-off-by: NGlauber Costa <glommer@parallels.com>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NGreg Thelen <gthelen@google.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Ying Han <yinghan@google.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      45cf7ebd
    • M
      mm: init: report on last-nid information stored in page->flags · a4e1b4c6
      Mel Gorman 提交于
      Answering the question "how much space remains in the page->flags" is
      time-consuming.  mminit_loglevel can help answer the question but it
      does not take last_nid information into account.  This patch corrects it
      and while there it corrects the messages related to page flag usage,
      pgshifts and node/zone id.  When applied the relevant output looks
      something like this but will depend on the kernel configuration.
      
        mminit::pageflags_layout_widths Section 0 Node 9 Zone 2 Lastnid 9 Flags 25
        mminit::pageflags_layout_shifts Section 19 Node 9 Zone 2 Lastnid 9
        mminit::pageflags_layout_pgshifts Section 0 Node 55 Zone 53 Lastnid 44
        mminit::pageflags_layout_nodezoneid Node/Zone ID: 64 -> 53
        mminit::pageflags_layout_usage location: 64 -> 44 layout 44 -> 25 unused 25 -> 0 page-flags
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a4e1b4c6
    • M
      mm: uninline page_xchg_last_nid() · 4468b8f1
      Mel Gorman 提交于
      Andrew Morton pointed out that page_xchg_last_nid() and
      reset_page_last_nid() were "getting nuttily large" and asked that it be
      investigated.
      
      reset_page_last_nid() is on the page free path and it would be
      unfortunate to make that path more expensive than it needs to be.  Due
      to the internal use of page_xchg_last_nid() it is already too expensive
      but fortunately, it should also be impossible for the page->flags to be
      updated in parallel when we call reset_page_last_nid().  Instead of
      unlining the function, it uses a simplier implementation that assumes no
      parallel updates and should now be sufficiently short for inlining.
      
      page_xchg_last_nid() is called in paths that are already quite expensive
      (splitting huge page, fault handling, migration) and it is reasonable to
      uninline.  There was not really a good place to place the function but
      mm/mmzone.c was the closest fit IMO.
      
      This patch saved 128 bytes of text in the vmlinux file for the kernel
      configuration I used for testing automatic NUMA balancing.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      4468b8f1
    • M
      memcg: clean up swap accounting initialization code · 6acc8b02
      Michal Hocko 提交于
      Memcg swap accounting is currently enabled by enable_swap_cgroup when
      the root cgroup is created.  mem_cgroup_init acts as a memcg subsystem
      initializer which sounds like a much better place for enable_swap_cgroup
      as well.  We already register memsw files from there so it makes a lot
      of sense to merge those two into a single enable_swap_cgroup function.
      
      This patch doesn't introduce any semantic changes.
      Signed-off-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Zhouping Liu <zliu@redhat.com>
      Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Li Zefan <lizefan@huawei.com>
      Cc: CAI Qian <caiqian@redhat.com>
      Cc: Tejun Heo <tj@kernel.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      6acc8b02
    • M
      memcg: do not create memsw files if swap accounting is disabled · 2d11085e
      Michal Hocko 提交于
      Zhouping Liu has reported that memsw files are exported even though swap
      accounting is runtime disabled if MEMCG_SWAP is enabled.  This behavior
      has been introduced by commit af36f906 ("memcg: always create memsw
      files if CGROUP_MEM_RES_CTLR_SWAP") and it causes any attempt to open
      the file to return EOPNOTSUPP.  Although EOPNOTSUPP should say be clear
      that memsw operations are not supported in the given configuration it is
      fair to say that this behavior could be quite confusing.
      
      Let's tear memsw files out of default cgroup files and add them only if
      the swap accounting is really enabled (either by MEMCG_SWAP_ENABLED or
      swapaccount=1 boot parameter).  We can hook into mem_cgroup_init which
      is called when the memcg subsystem is initialized and which happens
      after boot command line is processed.
      Signed-off-by: NMichal Hocko <mhocko@suse.cz>
      Reported-by: NZhouping Liu <zliu@redhat.com>
      Tested-by: NZhouping Liu <zliu@redhat.com>
      Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Li Zefan <lizefan@huawei.com>
      Cc: CAI Qian <caiqian@redhat.com>
      Cc: Tejun Heo <tj@kernel.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2d11085e
    • P
      page-writeback.c: subtract min_free_kbytes from dirtyable memory · 75f7ad8e
      Paul Szabo 提交于
      When calculating amount of dirtyable memory, min_free_kbytes should be
      subtracted because it is not intended for dirty pages.
      
      Addresses http://bugs.debian.org/695182
      
      [akpm@linux-foundation.org: fix up min_free_kbytes extern declarations]
      [akpm@linux-foundation.org: fix min() warning]
      Signed-off-by: NPaul Szabo <psz@maths.usyd.edu.au>
      Acked-by: NRik van Riel <riel@redhat.com>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      75f7ad8e
    • K
      mm/rmap: rename anon_vma_unlock() => anon_vma_unlock_write() · 08b52706
      Konstantin Khlebnikov 提交于
      The comment in commit 4fc3f1d6 ("mm/rmap, migration: Make
      rmap_walk_anon() and try_to_unmap_anon() more scalable") says:
      
      | Rename anon_vma_[un]lock() => anon_vma_[un]lock_write(),
      | to make it clearer that it's an exclusive write-lock in
      | that case - suggested by Rik van Riel.
      
      But that commit renames only anon_vma_lock()
      Signed-off-by: NKonstantin Khlebnikov <khlebnikov@openvz.org>
      Cc: Ingo Molnar <mingo@kernel.org>
      Reviewed-by: NRik van Riel <riel@redhat.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      08b52706
    • S
      swap: add per-partition lock for swapfile · ec8acf20
      Shaohua Li 提交于
      swap_lock is heavily contended when I test swap to 3 fast SSD (even
      slightly slower than swap to 2 such SSD).  The main contention comes
      from swap_info_get().  This patch tries to fix the gap with adding a new
      per-partition lock.
      
      Global data like nr_swapfiles, total_swap_pages, least_priority and
      swap_list are still protected by swap_lock.
      
      nr_swap_pages is an atomic now, it can be changed without swap_lock.  In
      theory, it's possible get_swap_page() finds no swap pages but actually
      there are free swap pages.  But sounds not a big problem.
      
      Accessing partition specific data (like scan_swap_map and so on) is only
      protected by swap_info_struct.lock.
      
      Changing swap_info_struct.flags need hold swap_lock and
      swap_info_struct.lock, because scan_scan_map() will check it.  read the
      flags is ok with either the locks hold.
      
      If both swap_lock and swap_info_struct.lock must be hold, we always hold
      the former first to avoid deadlock.
      
      swap_entry_free() can change swap_list.  To delete that code, we add a
      new highest_priority_index.  Whenever get_swap_page() is called, we
      check it.  If it's valid, we use it.
      
      It's a pity get_swap_page() still holds swap_lock().  But in practice,
      swap_lock() isn't heavily contended in my test with this patch (or I can
      say there are other much more heavier bottlenecks like TLB flush).  And
      BTW, looks get_swap_page() doesn't really need the lock.  We never free
      swap_info[] and we check SWAP_WRITEOK flag.  The only risk without the
      lock is we could swapout to some low priority swap, but we can quickly
      recover after several rounds of swap, so sounds not a big deal to me.
      But I'd prefer to fix this if it's a real problem.
      
      "swap: make each swap partition have one address_space" improved the
      swapout speed from 1.7G/s to 2G/s.  This patch further improves the
      speed to 2.3G/s, so around 15% improvement.  It's a multi-process test,
      so TLB flush isn't the biggest bottleneck before the patches.
      
      [arnd@arndb.de: fix it for nommu]
      [hughd@google.com: add missing unlock]
      [minchan@kernel.org: get rid of lockdep whinge on sys_swapon]
      Signed-off-by: NShaohua Li <shli@fusionio.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Minchan Kim <minchan.kim@gmail.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
      Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
      Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
      Cc: Stephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: NArnd Bergmann <arnd@arndb.de>
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Signed-off-by: NMinchan Kim <minchan@kernel.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      ec8acf20
    • S
      swap: make each swap partition have one address_space · 33806f06
      Shaohua Li 提交于
      When I use several fast SSD to do swap, swapper_space.tree_lock is
      heavily contended.  This makes each swap partition have one
      address_space to reduce the lock contention.  There is an array of
      address_space for swap.  The swap entry type is the index to the array.
      
      In my test with 3 SSD, this increases the swapout throughput 20%.
      
      [akpm@linux-foundation.org: revert unneeded change to  __add_to_swap_cache]
      Signed-off-by: NShaohua Li <shli@fusionio.com>
      Cc: Hugh Dickins <hughd@google.com>
      Acked-by: NRik van Riel <riel@redhat.com>
      Acked-by: NMinchan Kim <minchan@kernel.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      33806f06
    • S
      mm: don't inline page_mapping() · 9800339b
      Shaohua Li 提交于
      According to akpm, this saves 1/2k text and makes things simple for the
      next patch.
      
      Numbers from Minchan:
      
      add/remove: 1/0 grow/shrink: 6/22 up/down: 92/-516 (-424)
      function                                     old     new   delta
      page_mapping                                   -      48     +48
      do_task_stat                                2292    2308     +16
      page_remove_rmap                             240     248      +8
      load_elf_binary                             4500    4508      +8
      update_queue                                 532     536      +4
      scsi_probe_and_add_lun                      2892    2896      +4
      lookup_fast                                  644     648      +4
      vcs_read                                    1040    1036      -4
      __ip_route_output_key                       1904    1900      -4
      ip_route_input_noref                        2508    2500      -8
      shmem_file_aio_read                          784     772     -12
      __isolate_lru_page                           272     256     -16
      shmem_replace_page                           708     688     -20
      mark_buffer_dirty                            228     208     -20
      __set_page_dirty_buffers                     240     220     -20
      __remove_mapping                             276     256     -20
      update_mmu_cache                             500     476     -24
      set_page_dirty_balance                        92      68     -24
      set_page_dirty                               172     148     -24
      page_evictable                                88      64     -24
      page_cache_pipe_buf_steal                    248     224     -24
      clear_page_dirty_for_io                      340     316     -24
      test_set_page_writeback                      400     372     -28
      test_clear_page_writeback                    516     488     -28
      invalidate_inode_page                        156     128     -28
      page_mkclean                                 432     400     -32
      flush_dcache_page                            360     328     -32
      __set_page_dirty_nobuffers                   324     280     -44
      shrink_page_list                            2412    2356     -56
      Signed-off-by: NShaohua Li <shli@fusionio.com>
      Suggested-by: NAndrew Morton <akpm@linux-foundation.org>
      Cc: Hugh Dickins <hughd@google.com>
      Acked-by: NRik van Riel <riel@redhat.com>
      Cc: Minchan Kim <minchan.kim@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9800339b
    • H
      mm: numa: cleanup flow of transhuge page migration · 340ef390
      Hugh Dickins 提交于
      When correcting commit 04fa5d6a ("mm: migrate: check page_count of
      THP before migrating") Hugh Dickins noted that the control flow for
      transhuge migration was difficult to follow.  Unconditionally calling
      put_page() in numamigrate_isolate_page() made the failure paths of both
      migrate_misplaced_transhuge_page() and migrate_misplaced_page() more
      complex that they should be.  Further, he was extremely wary that an
      unlock_page() should ever happen after a put_page() even if the
      put_page() should never be the final put_page.
      
      Hugh implemented the following cleanup to simplify the path by calling
      putback_lru_page() inside numamigrate_isolate_page() if it failed to
      isolate and always calling unlock_page() within
      migrate_misplaced_transhuge_page().
      
      There is no functional change after this patch is applied but the code
      is easier to follow and unlock_page() always happens before put_page().
      
      [mgorman@suse.de: changelog only]
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      340ef390
    • P
      mm: fold page->_last_nid into page->flags where possible · 75980e97
      Peter Zijlstra 提交于
      page->_last_nid fits into page->flags on 64-bit.  The unlikely 32-bit
      NUMA configuration with NUMA Balancing will still need an extra page
      field.  As Peter notes "Completely dropping 32bit support for
      CONFIG_NUMA_BALANCING would simplify things, but it would also remove
      the warning if we grow enough 64bit only page-flags to push the last-cpu
      out."
      
      [mgorman@suse.de: minor modifications]
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
      Cc: Hugh Dickins <hughd@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      75980e97
    • P
      mm: move page flags layout to separate header · bbeae5b0
      Peter Zijlstra 提交于
      This is a preparation patch for moving page->_last_nid into page->flags
      that moves page flag layout information to a separate header.  This
      patch is necessary because otherwise there would be a circular
      dependency between mm_types.h and mm.h.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
      Cc: Hugh Dickins <hughd@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      bbeae5b0
    • M
      mm: numa: handle side-effects in count_vm_numa_events() for !CONFIG_NUMA_BALANCING · 3c0ff468
      Mel Gorman 提交于
      The current definitions for count_vm_numa_events() is wrong for
      !CONFIG_NUMA_BALANCING as the following would miss the side-effect.
      
      	count_vm_numa_events(NUMA_FOO, bar++);
      
      There are no such users of count_vm_numa_events() but this patch fixes
      it as it is a potential pitfall.  Ideally both would be converted to
      static inline but NUMA_PTE_UPDATES is not defined if
      !CONFIG_NUMA_BALANCING and creating dummy constants just to have a
      static inline would be similarly clumsy.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
      Cc: Hugh Dickins <hughd@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3c0ff468
    • M
      mm: numa: take THP into account when migrating pages for NUMA balancing · 3abef4e6
      Mel Gorman 提交于
      Wanpeng Li pointed out that numamigrate_isolate_page() assumes that only
      one base page is being migrated when in fact it can also be checking
      THP.
      
      The consequences are that a migration will be attempted when a target
      node is nearly full and fail later.  It's unlikely to be user-visible
      but it should be fixed.  While we are there, migrate_balanced_pgdat()
      should treat nr_migrate_pages as an unsigned long as it is treated as a
      watermark.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Suggested-by: NWanpeng Li <liwanp@linux.vnet.ibm.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Cc: Hugh Dickins <hughd@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3abef4e6
    • M
      mm: numa: fix minor typo in numa_next_scan · 34f0315a
      Mel Gorman 提交于
      s/me/be/ and clarify the comment a bit when we're changing it anyway.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Suggested-by: NSimon Jeons <simon.jeons@gmail.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
      Cc: Hugh Dickins <hughd@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      34f0315a
    • K
    • M
      usb: forbid memory allocation with I/O during bus reset · 4d769def
      Ming Lei 提交于
      If one storage interface or usb network interface(iSCSI case) exists in
      current configuration, memory allocation with GFP_KERNEL during
      usb_device_reset() might trigger I/O transfer on the storage interface
      itself and cause deadlock because the 'us->dev_mutex' is held in
      .pre_reset() and the storage interface can't do I/O transfer when the
      reset is triggered by other interface, or the error handling can't be
      completed if the reset is triggered by the storage itself (error
      handling path).
      Signed-off-by: NMing Lei <ming.lei@canonical.com>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: David Decotigny <david.decotigny@google.com>
      Cc: Tom Herbert <therbert@google.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Alan Stern <stern@rowland.harvard.edu>
      Cc: Oliver Neukum <oneukum@suse.de>
      Reviewed-by: NJiri Kosina <jkosina@suse.cz>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
      Cc: Greg KH <greg@kroah.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      4d769def
    • M
      pm / runtime: force memory allocation with no I/O during Runtime PM callbcack · db88175f
      Ming Lei 提交于
      Apply the introduced memalloc_noio_save() and memalloc_noio_restore() to
      force memory allocation with no I/O during runtime_resume/runtime_suspend
      callback on device with the flag of 'memalloc_noio' set.
      Signed-off-by: NMing Lei <ming.lei@canonical.com>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: David Decotigny <david.decotigny@google.com>
      Cc: Tom Herbert <therbert@google.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Alan Stern <stern@rowland.harvard.edu>
      Cc: Oliver Neukum <oneukum@suse.de>
      Cc: Jiri Kosina <jiri.kosina@suse.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
      Cc: Greg KH <greg@kroah.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      db88175f
    • M
      net/core: apply pm_runtime_set_memalloc_noio on network devices · 9802c8e2
      Ming Lei 提交于
      Deadlock might be caused by allocating memory with GFP_KERNEL in
      runtime_resume and runtime_suspend callback of network devices in iSCSI
      situation, so mark network devices and its ancestor as 'memalloc_noio'
      with the introduced pm_runtime_set_memalloc_noio().
      Signed-off-by: NMing Lei <ming.lei@canonical.com>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: David Decotigny <david.decotigny@google.com>
      Cc: Tom Herbert <therbert@google.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Alan Stern <stern@rowland.harvard.edu>
      Cc: Oliver Neukum <oneukum@suse.de>
      Cc: Jiri Kosina <jiri.kosina@suse.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
      Cc: Greg KH <greg@kroah.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9802c8e2
    • M
      block/genhd.c: apply pm_runtime_set_memalloc_noio on block devices · 25e823c8
      Ming Lei 提交于
      Apply the introduced pm_runtime_set_memalloc_noio on block device so
      that PM core will teach mm to not allocate memory with GFP_IOFS when
      calling the runtime_resume and runtime_suspend callback for block
      devices and its ancestors.
      Signed-off-by: NMing Lei <ming.lei@canonical.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Alan Stern <stern@rowland.harvard.edu>
      Cc: Oliver Neukum <oneukum@suse.de>
      Cc: Jiri Kosina <jiri.kosina@suse.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
      Cc: Greg KH <greg@kroah.com>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: David Decotigny <david.decotigny@google.com>
      Cc: Tom Herbert <therbert@google.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      25e823c8
    • M
      pm / runtime: introduce pm_runtime_set_memalloc_noio() · e823407f
      Ming Lei 提交于
      Introduce the flag memalloc_noio in 'struct dev_pm_info' to help PM core
      to teach mm not allocating memory with GFP_KERNEL flag for avoiding
      probable deadlock.
      
      As explained in the comment, any GFP_KERNEL allocation inside
      runtime_resume() or runtime_suspend() on any one of device in the path
      from one block or network device to the root device in the device tree
      may cause deadlock, the introduced pm_runtime_set_memalloc_noio() sets
      or clears the flag on device in the path recursively.
      Signed-off-by: NMing Lei <ming.lei@canonical.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Alan Stern <stern@rowland.harvard.edu>
      Cc: Oliver Neukum <oneukum@suse.de>
      Cc: Jiri Kosina <jiri.kosina@suse.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
      Cc: Greg KH <greg@kroah.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: David Decotigny <david.decotigny@google.com>
      Cc: Tom Herbert <therbert@google.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e823407f
    • M
      mm: teach mm by current context info to not do I/O during memory allocation · 21caf2fc
      Ming Lei 提交于
      This patch introduces PF_MEMALLOC_NOIO on process flag('flags' field of
      'struct task_struct'), so that the flag can be set by one task to avoid
      doing I/O inside memory allocation in the task's context.
      
      The patch trys to solve one deadlock problem caused by block device, and
      the problem may happen at least in the below situations:
      
      - during block device runtime resume, if memory allocation with
        GFP_KERNEL is called inside runtime resume callback of any one of its
        ancestors(or the block device itself), the deadlock may be triggered
        inside the memory allocation since it might not complete until the block
        device becomes active and the involed page I/O finishes.  The situation
        is pointed out first by Alan Stern.  It is not a good approach to
        convert all GFP_KERNEL[1] in the path into GFP_NOIO because several
        subsystems may be involved(for example, PCI, USB and SCSI may be
        involved for usb mass stoarage device, network devices involved too in
        the iSCSI case)
      
      - during block device runtime suspend, because runtime resume need to
        wait for completion of concurrent runtime suspend.
      
      - during error handling of usb mass storage deivce, USB bus reset will
        be put on the device, so there shouldn't have any memory allocation with
        GFP_KERNEL during USB bus reset, otherwise the deadlock similar with
        above may be triggered.  Unfortunately, any usb device may include one
        mass storage interface in theory, so it requires all usb interface
        drivers to handle the situation.  In fact, most usb drivers don't know
        how to handle bus reset on the device and don't provide .pre_set() and
        .post_reset() callback at all, so USB core has to unbind and bind driver
        for these devices.  So it is still not practical to resort to GFP_NOIO
        for solving the problem.
      
      Also the introduced solution can be used by block subsystem or block
      drivers too, for example, set the PF_MEMALLOC_NOIO flag before doing
      actual I/O transfer.
      
      It is not a good idea to convert all these GFP_KERNEL in the affected
      path into GFP_NOIO because these functions doing that may be implemented
      as library and will be called in many other contexts.
      
      In fact, memalloc_noio_flags() can convert some of current static
      GFP_NOIO allocation into GFP_KERNEL back in other non-affected contexts,
      at least almost all GFP_NOIO in USB subsystem can be converted into
      GFP_KERNEL after applying the approach and make allocation with GFP_NOIO
      only happen in runtime resume/bus reset/block I/O transfer contexts
      generally.
      
      [1], several GFP_KERNEL allocation examples in runtime resume path
      
      - pci subsystem
      acpi_os_allocate
      	<-acpi_ut_allocate
      		<-ACPI_ALLOCATE_ZEROED
      			<-acpi_evaluate_object
      				<-__acpi_bus_set_power
      					<-acpi_bus_set_power
      						<-acpi_pci_set_power_state
      							<-platform_pci_set_power_state
      								<-pci_platform_power_transition
      									<-__pci_complete_power_transition
      										<-pci_set_power_state
      											<-pci_restore_standard_config
      												<-pci_pm_runtime_resume
      - usb subsystem
      usb_get_status
      	<-finish_port_resume
      		<-usb_port_resume
      			<-generic_resume
      				<-usb_resume_device
      					<-usb_resume_both
      						<-usb_runtime_resume
      
      - some individual usb drivers
      usblp, uvc, gspca, most of dvb-usb-v2 media drivers, cpia2, az6007, ....
      
      That is just what I have found.  Unfortunately, this allocation can only
      be found by human being now, and there should be many not found since
      any function in the resume path(call tree) may allocate memory with
      GFP_KERNEL.
      Signed-off-by: NMing Lei <ming.lei@canonical.com>
      Signed-off-by: NMinchan Kim <minchan@kernel.org>
      Cc: Alan Stern <stern@rowland.harvard.edu>
      Cc: Oliver Neukum <oneukum@suse.de>
      Cc: Jiri Kosina <jiri.kosina@suse.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
      Cc: Greg KH <greg@kroah.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: David Decotigny <david.decotigny@google.com>
      Cc: Tom Herbert <therbert@google.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      21caf2fc
    • Z
      mm: don't wait on congested zones in balance_pgdat() · 258401a6
      Zlatko Calusic 提交于
      From: Zlatko Calusic <zlatko.calusic@iskon.hr>
      
      Commit 92df3a72 ("mm: vmscan: throttle reclaim if encountering too
      many dirty pages under writeback") introduced waiting on congested zones
      based on a sane algorithm in shrink_inactive_list().
      
      What this means is that there's no more need for throttling and
      additional heuristics in balance_pgdat().  So, let's remove it and tidy
      up the code.
      Signed-off-by: NZlatko Calusic <zlatko.calusic@iskon.hr>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Minchan Kim <minchan.kim@gmail.com>
      Cc: Johannes Weiner <jweiner@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      258401a6