1. 08 5月, 2007 15 次提交
    • C
      slab allocators: Remove SLAB_CTOR_ATOMIC · 4f104934
      Christoph Lameter 提交于
      SLAB_CTOR atomic is never used which is no surprise since I cannot imagine
      that one would want to do something serious in a constructor or destructor.
       In particular given that the slab allocators run with interrupts disabled.
       Actions in constructors and destructors are by their nature very limited
      and usually do not go beyond initializing variables and list operations.
      
      (The i386 pgd ctor and dtors do take a spinlock in constructor and
      destructor.....  I think that is the furthest we go at this point.)
      
      There is no flag passed to the destructor so removing SLAB_CTOR_ATOMIC also
      establishes a certain symmetry.
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      4f104934
    • C
      slab allocators: Remove SLAB_DEBUG_INITIAL flag · 50953fe9
      Christoph Lameter 提交于
      I have never seen a use of SLAB_DEBUG_INITIAL.  It is only supported by
      SLAB.
      
      I think its purpose was to have a callback after an object has been freed
      to verify that the state is the constructor state again?  The callback is
      performed before each freeing of an object.
      
      I would think that it is much easier to check the object state manually
      before the free.  That also places the check near the code object
      manipulation of the object.
      
      Also the SLAB_DEBUG_INITIAL callback is only performed if the kernel was
      compiled with SLAB debugging on.  If there would be code in a constructor
      handling SLAB_DEBUG_INITIAL then it would have to be conditional on
      SLAB_DEBUG otherwise it would just be dead code.  But there is no such code
      in the kernel.  I think SLUB_DEBUG_INITIAL is too problematic to make real
      use of, difficult to understand and there are easier ways to accomplish the
      same effect (i.e.  add debug code before kfree).
      
      There is a related flag SLAB_CTOR_VERIFY that is frequently checked to be
      clear in fs inode caches.  Remove the pointless checks (they would even be
      pointless without removeal of SLAB_DEBUG_INITIAL) from the fs constructors.
      
      This is the last slab flag that SLUB did not support.  Remove the check for
      unimplemented flags from SLUB.
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      50953fe9
    • C
      slab allocators: Remove obsolete SLAB_MUST_HWCACHE_ALIGN · 5af60839
      Christoph Lameter 提交于
      This patch was recently posted to lkml and acked by Pekka.
      
      The flag SLAB_MUST_HWCACHE_ALIGN is
      
      1. Never checked by SLAB at all.
      
      2. A duplicate of SLAB_HWCACHE_ALIGN for SLUB
      
      3. Fulfills the role of SLAB_HWCACHE_ALIGN for SLOB.
      
      The only remaining use is in sparc64 and ppc64 and their use there
      reflects some earlier role that the slab flag once may have had. If
      its specified then SLAB_HWCACHE_ALIGN is also specified.
      
      The flag is confusing, inconsistent and has no purpose.
      
      Remove it.
      Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      5af60839
    • C
      slub: remove object activities out of checking functions · 70d71228
      Christoph Lameter 提交于
      Make sure that the check function really only check things and do not perform
      activities.  Extract the tracing and object seeding out of the two check
      functions and place them into slab_alloc and slab_free
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      70d71228
    • C
      SLUB: Free slabs and sort partial slab lists in kmem_cache_shrink · 2086d26a
      Christoph Lameter 提交于
      At kmem_cache_shrink check if we have any empty slabs on the partial
      if so then remove them.
      
      Also--as an anti-fragmentation measure--sort the partial slabs so that
      the most fully allocated ones come first and the least allocated last.
      
      The next allocations may fill up the nearly full slabs. Having the
      least allocated slabs last gives them the maximum chance that their
      remaining objects may be freed. Thus we can hopefully minimize the
      partial slabs.
      
      I think this is the best one can do in terms antifragmentation
      measures. Real defragmentation (meaning moving objects out of slabs with
      the least free objects to those that are almost full) can be implemted
      by reverse scanning through the list produced here but that would mean
      that we need to provide a callback at slab cache creation that allows
      the deletion or moving of an object. This will involve slab API
      changes, so defer for now.
      
      Cc: Mel Gorman <mel@skynet.ie>
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2086d26a
    • C
      slub: add ability to list alloc / free callers per slab · 88a420e4
      Christoph Lameter 提交于
      This patch enables listing the callers who allocated or freed objects in a
      cache.
      
      For example to list the allocators for kmalloc-128 do
      
      cat /sys/slab/kmalloc-128/alloc_calls
            7 sn_io_slot_fixup+0x40/0x700
            7 sn_io_slot_fixup+0x80/0x700
            9 sn_bus_fixup+0xe0/0x380
            6 param_sysfs_setup+0xf0/0x280
          276 percpu_populate+0xf0/0x1a0
           19 __register_chrdev_region+0x30/0x360
            8 expand_files+0x2e0/0x6e0
            1 sys_epoll_create+0x60/0x200
            1 __mounts_open+0x140/0x2c0
           65 kmem_alloc+0x110/0x280
            3 alloc_disk_node+0xe0/0x200
           33 as_get_io_context+0x90/0x280
           74 kobject_kset_add_dir+0x40/0x140
           12 pci_create_bus+0x2a0/0x5c0
            1 acpi_ev_create_gpe_block+0x120/0x9e0
           41 con_insert_unipair+0x100/0x1c0
            1 uart_open+0x1c0/0xba0
            1 dma_pool_create+0xe0/0x340
            2 neigh_table_init_no_netlink+0x260/0x4c0
            6 neigh_parms_alloc+0x30/0x200
            1 netlink_kernel_create+0x130/0x320
            5 fz_hash_alloc+0x50/0xe0
            2 sn_common_hubdev_init+0xd0/0x6e0
           28 kernel_param_sysfs_setup+0x30/0x180
           72 process_zones+0x70/0x2e0
      
      cat /sys/slab/kmalloc-128/free_calls
          558 <not-available>
            3 sn_io_slot_fixup+0x600/0x700
           84 free_fdtable_rcu+0x120/0x260
            2 seq_release+0x40/0x60
            6 kmem_free+0x70/0xc0
           24 free_as_io_context+0x20/0x200
            1 acpi_get_object_info+0x3a0/0x3e0
            1 acpi_add_single_object+0xcf0/0x1e40
            2 con_release_unimap+0x80/0x140
            1 free+0x20/0x40
      
      SLAB_STORE_USER must be enabled for a slab cache by either booting with
      "slab_debug" or enabling user tracking specifically for the slab of interest.
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      88a420e4
    • C
      SLUB: Add MIN_PARTIAL · e95eed57
      Christoph Lameter 提交于
      We leave a mininum of partial slabs on nodes when we search for
      partial slabs on other node. Define a constant for that value.
      
      Then modify slub to keep MIN_PARTIAL slabs around.
      
      This avoids bad situations where a function frees the last object
      in a slab (which results in the page being returned to the page
      allocator) only to then allocate one again (which requires getting
      a page back from the page allocator if the partial list was empty).
      Keeping a couple of slabs on the partial list reduces overhead.
      
      Empty slabs are added to the end of the partial list to insure that
      partially allocated slabs are consumed first (defragmentation).
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e95eed57
    • C
      slub: validation of slabs (metadata and guard zones) · 53e15af0
      Christoph Lameter 提交于
      This enables validation of slab.  Validation means that all objects are
      checked to see if there are redzone violations, if padding has been
      overwritten or any pointers have been corrupted.  Also checks the consistency
      of slab counters.
      
      Validation enables the detection of metadata corruption without the kernel
      having to execute code that actually uses (allocs/frees) and object.  It
      allows one to make sure that the slab metainformation and the guard values
      around an object have not been compromised.
      
      A single slabcache can be checked by writing a 1 to the "validate" file.
      
      i.e.
      
      echo 1 >/sys/slab/kmalloc-128/validate
      
      or use the slabinfo tool to check all slabs
      
      slabinfo -v
      
      Error messages will show up in the syslog.
      
      Note that validation can only reach slabs that are on a list.  This means that
      we are usually restricted to partial slabs and active slabs unless
      SLAB_STORE_USER is active which will build a full slab list and allows
      validation of slabs that are fully in use.  Booting with "slub_debug" set will
      enable SLAB_STORE_USER and then full diagnostic are available.
      
      Note that we attempt to push cpu slabs back to the lists when we start the
      check.  If the cpu slab is reactivated before we get to it (another processor
      grabs it before we get to it) then it cannot be checked.
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      53e15af0
    • C
      slub: enable tracking of full slabs · 643b1138
      Christoph Lameter 提交于
      If slab tracking is on then build a list of full slabs so that we can verify
      the integrity of all slabs and are also able to built list of alloc/free
      callers.
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      643b1138
    • C
      slub: fix object tracking · 77c5e2d0
      Christoph Lameter 提交于
      Object tracking did not work the right way for several call chains. Fix this up
      by adding a new parameter to slub_alloc and slub_free that specifies the
      caller address explicitly.
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      77c5e2d0
    • C
    • C
      Make page->private usable in compound pages · d85f3385
      Christoph Lameter 提交于
      If we add a new flag so that we can distinguish between the first page and the
      tail pages then we can avoid to use page->private in the first page.
      page->private == page for the first page, so there is no real information in
      there.
      
      Freeing up page->private makes the use of compound pages more transparent.
      They become more usable like real pages.  Right now we have to be careful f.e.
       if we are going beyond PAGE_SIZE allocations in the slab on i386 because we
      can then no longer use the private field.  This is one of the issues that
      cause us not to support debugging for page size slabs in SLAB.
      
      Having page->private available for SLUB would allow more meta information in
      the page struct.  I can probably avoid the 16 bit ints that I have in there
      right now.
      
      Also if page->private is available then a compound page may be equipped with
      buffer heads.  This may free up the way for filesystems to support larger
      blocks than page size.
      
      We add PageTail as an alias of PageReclaim.  Compound pages cannot currently
      be reclaimed.  Because of the alias one needs to check PageCompound first.
      
      The RFC for the this approach was discussed at
      http://marc.info/?t=117574302800001&r=1&w=2
      
      [nacc@us.ibm.com: fix hugetlbfs]
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NNishanth Aravamudan <nacc@us.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d85f3385
    • C
      SLUB: allocate smallest object size if the user asks for 0 bytes · 614410d5
      Christoph Lameter 提交于
      Makes SLUB behave like SLAB in this area to avoid issues....
      
      Throw a stack dump to alert people.
      
      At some point the behavior should be switched back.  NULL is no memory as
      far as I can tell and if the use asked for 0 bytes then he need to get no
      memory.
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      614410d5
    • C
      SLUB: change default alignments · 47bfdc0d
      Christoph Lameter 提交于
      Structures may contain u64 items on 32 bit platforms that are only able to
      address 64 bit items on 64 bit boundaries.  Change the mininum alignment of
      slabs to conform to those expectations.
      
      ARCH_KMALLOC_MINALIGN must be changed for good since a variety of structure
      are mixed in the general slabs.
      
      ARCH_SLAB_MINALIGN is changed because currently there is no consistent
      specification of object alignment.  We may have that in the future when the
      KMEM_CACHE and related macros are used to generate slabs.  These pass the
      alignment of the structure generated by the compiler to the slab.
      
      With KMEM_CACHE etc we could align structures that do not contain 64
      bit values to 32 bit boundaries potentially saving some memory.
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      47bfdc0d
    • C
      SLUB core · 81819f0f
      Christoph Lameter 提交于
      This is a new slab allocator which was motivated by the complexity of the
      existing code in mm/slab.c. It attempts to address a variety of concerns
      with the existing implementation.
      
      A. Management of object queues
      
         A particular concern was the complex management of the numerous object
         queues in SLAB. SLUB has no such queues. Instead we dedicate a slab for
         each allocating CPU and use objects from a slab directly instead of
         queueing them up.
      
      B. Storage overhead of object queues
      
         SLAB Object queues exist per node, per CPU. The alien cache queue even
         has a queue array that contain a queue for each processor on each
         node. For very large systems the number of queues and the number of
         objects that may be caught in those queues grows exponentially. On our
         systems with 1k nodes / processors we have several gigabytes just tied up
         for storing references to objects for those queues  This does not include
         the objects that could be on those queues. One fears that the whole
         memory of the machine could one day be consumed by those queues.
      
      C. SLAB meta data overhead
      
         SLAB has overhead at the beginning of each slab. This means that data
         cannot be naturally aligned at the beginning of a slab block. SLUB keeps
         all meta data in the corresponding page_struct. Objects can be naturally
         aligned in the slab. F.e. a 128 byte object will be aligned at 128 byte
         boundaries and can fit tightly into a 4k page with no bytes left over.
         SLAB cannot do this.
      
      D. SLAB has a complex cache reaper
      
         SLUB does not need a cache reaper for UP systems. On SMP systems
         the per CPU slab may be pushed back into partial list but that
         operation is simple and does not require an iteration over a list
         of objects. SLAB expires per CPU, shared and alien object queues
         during cache reaping which may cause strange hold offs.
      
      E. SLAB has complex NUMA policy layer support
      
         SLUB pushes NUMA policy handling into the page allocator. This means that
         allocation is coarser (SLUB does interleave on a page level) but that
         situation was also present before 2.6.13. SLABs application of
         policies to individual slab objects allocated in SLAB is
         certainly a performance concern due to the frequent references to
         memory policies which may lead a sequence of objects to come from
         one node after another. SLUB will get a slab full of objects
         from one node and then will switch to the next.
      
      F. Reduction of the size of partial slab lists
      
         SLAB has per node partial lists. This means that over time a large
         number of partial slabs may accumulate on those lists. These can
         only be reused if allocator occur on specific nodes. SLUB has a global
         pool of partial slabs and will consume slabs from that pool to
         decrease fragmentation.
      
      G. Tunables
      
         SLAB has sophisticated tuning abilities for each slab cache. One can
         manipulate the queue sizes in detail. However, filling the queues still
         requires the uses of the spin lock to check out slabs. SLUB has a global
         parameter (min_slab_order) for tuning. Increasing the minimum slab
         order can decrease the locking overhead. The bigger the slab order the
         less motions of pages between per CPU and partial lists occur and the
         better SLUB will be scaling.
      
      G. Slab merging
      
         We often have slab caches with similar parameters. SLUB detects those
         on boot up and merges them into the corresponding general caches. This
         leads to more effective memory use. About 50% of all caches can
         be eliminated through slab merging. This will also decrease
         slab fragmentation because partial allocated slabs can be filled
         up again. Slab merging can be switched off by specifying
         slub_nomerge on boot up.
      
         Note that merging can expose heretofore unknown bugs in the kernel
         because corrupted objects may now be placed differently and corrupt
         differing neighboring objects. Enable sanity checks to find those.
      
      H. Diagnostics
      
         The current slab diagnostics are difficult to use and require a
         recompilation of the kernel. SLUB contains debugging code that
         is always available (but is kept out of the hot code paths).
         SLUB diagnostics can be enabled via the "slab_debug" option.
         Parameters can be specified to select a single or a group of
         slab caches for diagnostics. This means that the system is running
         with the usual performance and it is much more likely that
         race conditions can be reproduced.
      
      I. Resiliency
      
         If basic sanity checks are on then SLUB is capable of detecting
         common error conditions and recover as best as possible to allow the
         system to continue.
      
      J. Tracing
      
         Tracing can be enabled via the slab_debug=T,<slabcache> option
         during boot. SLUB will then protocol all actions on that slabcache
         and dump the object contents on free.
      
      K. On demand DMA cache creation.
      
         Generally DMA caches are not needed. If a kmalloc is used with
         __GFP_DMA then just create this single slabcache that is needed.
         For systems that have no ZONE_DMA requirement the support is
         completely eliminated.
      
      L. Performance increase
      
         Some benchmarks have shown speed improvements on kernbench in the
         range of 5-10%. The locking overhead of slub is based on the
         underlying base allocation size. If we can reliably allocate
         larger order pages then it is possible to increase slub
         performance much further. The anti-fragmentation patches may
         enable further performance increases.
      
      Tested on:
      i386 UP + SMP, x86_64 UP + SMP + NUMA emulation, IA64 NUMA + Simulator
      
      SLUB Boot options
      
      slub_nomerge		Disable merging of slabs
      slub_min_order=x	Require a minimum order for slab caches. This
      			increases the managed chunk size and therefore
      			reduces meta data and locking overhead.
      slub_min_objects=x	Mininum objects per slab. Default is 8.
      slub_max_order=x	Avoid generating slabs larger than order specified.
      slub_debug		Enable all diagnostics for all caches
      slub_debug=<options>	Enable selective options for all caches
      slub_debug=<o>,<cache>	Enable selective options for a certain set of
      			caches
      
      Available Debug options
      F		Double Free checking, sanity and resiliency
      R		Red zoning
      P		Object / padding poisoning
      U		Track last free / alloc
      T		Trace all allocs / frees (only use for individual slabs).
      
      To use SLUB: Apply this patch and then select SLUB as the default slab
      allocator.
      
      [hugh@veritas.com: fix an oops-causing locking error]
      [akpm@linux-foundation.org: various stupid cleanups and small fixes]
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Signed-off-by: NHugh Dickins <hugh@veritas.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      81819f0f