The patch halves space occupied by compound_dtor and compound_order in
struct page.

For compound_order, it's trivial long -> short conversion.

For get_compound_page_dtor(), we now use hardcoded table for destructor
lookup and store its index in the struct page instead of direct pointer
to destructor. It shouldn't be a big trouble to maintain the table: we
have only two destructor and NULL currently.

This patch free up one word in tail pages for reuse. This is preparation
for the next patch.
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NAndrea Arcangeli <aarcange@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We are going to rework how compound_head() work. It will not use
page->first_page as we have it now.

The only other user of page->first_page beyond compound pages is
zsmalloc.

Let's use page->private instead of page->first_page here. It occupies
the same storage space.
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: NAndrea Arcangeli <aarcange@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We have properly typed page->rcu_head, no need to cast page->lru.
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: NAndrea Arcangeli <aarcange@redhat.com>
Acked-by: NChristoph Lameter <cl@linux.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since 8456a648 ("slab: use struct page for slab management") nobody
uses slab_page field in struct page.

Let's drop it.
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: NChristoph Lameter <cl@linux.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NAndrea Arcangeli <aarcange@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Each `struct size_class' contains `struct zs_size_stat': an array of
NR_ZS_STAT_TYPE `unsigned long'.  For zsmalloc built with no
CONFIG_ZSMALLOC_STAT this results in a waste of `2 * sizeof(unsigned
long)' per-class.

The patch removes unneeded `struct zs_size_stat' members by redefining
NR_ZS_STAT_TYPE (max stat idx in array).

Since both NR_ZS_STAT_TYPE and zs_stat_type are compile time constants,
GCC can eliminate zs_stat_inc()/zs_stat_dec() calls that use zs_stat_type
larger than NR_ZS_STAT_TYPE: CLASS_ALMOST_EMPTY and CLASS_ALMOST_FULL at
the moment.

./scripts/bloat-o-meter mm/zsmalloc.o.old mm/zsmalloc.o.new
add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-39 (-39)
function                                     old     new   delta
fix_fullness_group                            97      94      -3
insert_zspage                                100      86     -14
remove_zspage                                141     119     -22

To summarize:
a) each class now uses less memory
b) we avoid a number of dec/inc stats (a minor optimization,
   but still).

The gain will increase once we introduce additional stats.

A simple IO test.

iozone -t 4 -R -r 32K -s 60M -I +Z
                        patched                 base
"  Initial write "       4145599.06              4127509.75
"        Rewrite "       4146225.94              4223618.50
"           Read "      17157606.00             17211329.50
"        Re-read "      17380428.00             17267650.50
"   Reverse Read "      16742768.00             16162732.75
"    Stride read "      16586245.75             16073934.25
"    Random read "      16349587.50             15799401.75
" Mixed workload "      10344230.62              9775551.50
"   Random write "       4277700.62              4260019.69
"         Pwrite "       4302049.12              4313703.88
"          Pread "       6164463.16              6126536.72
"         Fwrite "       7131195.00              6952586.00
"          Fread "      12682602.25             12619207.50
Signed-off-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NHui Zhu <zhuhui@xiaomi.com>
Reviewed-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We don't let user to disable shrinker in zsmalloc (once it's been
enabled), so no need to check ->shrinker_enabled in zs_shrinker_count(),
at the moment at least.
Signed-off-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.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>

A cosmetic change.

Commit c60369f0 ("staging: zsmalloc: prevent mappping in interrupt
context") added in_interrupt() check to zs_map_object() and 'hardirq.h'
include; but in_interrupt() macro is defined in 'preempt.h' not in
'hardirq.h', so include it instead.
Signed-off-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.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>

In obj_malloc():

	if (!class->huge)
		/* record handle in the header of allocated chunk */
		link->handle = handle;
	else
		/* record handle in first_page->private */
		set_page_private(first_page, handle);

In the hugepage we save handle to private directly.

But in obj_to_head():

	if (class->huge) {
		VM_BUG_ON(!is_first_page(page));
		return *(unsigned long *)page_private(page);
	} else
		return *(unsigned long *)obj;

It is used as a pointer.

The reason why there is no problem until now is huge-class page is born
with ZS_FULL so it can't be migrated.  However, we need this patch for
future work: "VM-aware zsmalloced page migration" to reduce external
fragmentation.
Signed-off-by: NHui Zhu <zhuhui@xiaomi.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

[akpm@linux-foundation.org: fix grammar]
Signed-off-by: NHui Zhu <zhuhui@xiaomi.com>
Reviewed-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Constify `struct zs_pool' ->name.

[akpm@inux-foundation.org: constify zpool_create_pool()'s `type' arg also]
Signed-off-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: NDan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Make the return type of zpool_get_type const; the string belongs to the
zpool driver and should not be modified.  Remove the redundant type field
in the struct zpool; it is private to zpool.c and isn't needed since
->driver->type can be used directly.  Add comments indicating strings must
be null-terminated.
Signed-off-by: NDan Streetman <ddstreet@ieee.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Instead of using a fixed-length string for the zswap params, use charp.
This simplifies the code and uses less memory, as most zswap param strings
will be less than the current maximum length.
Signed-off-by: NDan Streetman <ddstreet@ieee.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Seth Jennings <sjennings@variantweb.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Change the param_free_charp() function from static to exported.

It is used by zswap in the next patch ("zswap: use charp for zswap param
strings").
Signed-off-by: NDan Streetman <ddstreet@ieee.org>
Acked-by: NRusty Russell <rusty@rustcorp.com.au>
Cc: Seth Jennings <sjennings@variantweb.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

On the next line entry variable will be re-initialized so no need to init
it with NULL.
Signed-off-by: NAlexey Klimov <alexey.klimov@linaro.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Make is_partial_io()/valid_io_request()/page_zero_filled() return boolean,
since each function only uses either one or zero as its return value.
Signed-off-by: NGeliang Tang <geliangtang@163.com>
Reviewed-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

`mem_used_max' is designed to store the max amount of memory zram consumed
to store the data.  However, it does not represent the actual
'overcommited' (max) value.  The existing code goes to -ENOMEM
overcommited case before it updates `->stats.max_used_pages', which hides
the reason we went to -ENOMEM in the first place -- we actually used more
memory than `->limit_pages':

        alloced_pages = zs_get_total_pages(meta->mem_pool);
        if (zram->limit_pages && alloced_pages > zram->limit_pages) {
                zs_free(meta->mem_pool, handle);
                ret = -ENOMEM;
                goto out;
        }

        update_used_max(zram, alloced_pages);

Which is misleading.  User will see -ENOMEM, check `->limit_pages', check
`->stats.max_used_pages', which will keep the value BEFORE zram passed
`->limit_pages', and see:
	`->stats.max_used_pages' < `->limit_pages'

Move update_used_max() before we do `->limit_pages' check, so that
user will see:
	`->stats.max_used_pages' > `->limit_pages'
should the overcommit and -ENOMEM happen.
Signed-off-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.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>

When the user supplies an unsupported compression algorithm, keep the
previously selected one (knowingly supported) or the default one (if the
compression algorithm hasn't been changed yet).

Note that previously this operation (i.e. setting an invalid algorithm)
would result in no algorithm being selected, which means that this
represents a small change in the default behaviour.

Minchan said:

For initializing zram, we need to set up 3 optional parameters in advance.

1. the number of compression streams
2. memory limitation
3. compression algorithm

Although user pass completely wrong value to set up for 1 and 2
parameters, it's okay because they have default value so zram will be
initialized with the default value (of course, when user passes a wrong
value via *echo*, sysfs returns -EINVAL so the user can notice it).

But 3 is not consistent with other optional parameters.  IOW, if the
user passes a wrong value to set up 3 parameter, zram's initialization
would fail unlike other optional parameters.

So this patch makes them consistent.
Signed-off-by: NLuis Henriques <luis.henriques@canonical.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

gcc version 5.2.1 20151010 (Debian 5.2.1-22)
$ size mm/memcontrol.o mm/memcontrol.o.before
   text    data     bss     dec     hex filename
  35535    7908      64   43507    a9f3 mm/memcontrol.o
  35762    7908      64   43734    aad6 mm/memcontrol.o.before

Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

sync_file_range(2) is documented to issue writeback only for pages that
are not currently being written.  After all the system call has been
created for userspace to be able to issue background writeout and so
waiting for in-flight IO is undesirable there.  However commit
ee53a891 ("mm: do_sync_mapping_range integrity fix") switched
do_sync_mapping_range() and thus sync_file_range() to issue writeback in
WB_SYNC_ALL mode since do_sync_mapping_range() was used by other code
relying on WB_SYNC_ALL semantics.

These days do_sync_mapping_range() went away and we can switch
sync_file_range(2) back to issuing WB_SYNC_NONE writeback.  That should
help PostgreSQL avoid large latency spikes when flushing data in the
background.

Andres measured a 20% increase in transactions per second on an SSD disk.
Signed-off-by: NJan Kara <jack@suse.com>
Reported-by: NAndres Freund <andres@anarazel.de>
Tested-By: NAndres Freund <andres@anarazel.de>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The "vma" parameter to khugepaged_alloc_page() is unused.  It has to
remain unused or the drop read lock 'map_sem' optimisation introduce by
commit 8b164568 ("mm, THP: don't hold mmap_sem in khugepaged when
allocating THP") wouldn't be safe.  So let's remove it.
Signed-off-by: NAaron Tomlin <atomlin@redhat.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There are many places which use mapping_gfp_mask to restrict a more
generic gfp mask which would be used for allocations which are not
directly related to the page cache but they are performed in the same
context.

Let's introduce a helper function which makes the restriction explicit and
easier to track.  This patch doesn't introduce any functional changes.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NMichal Hocko <mhocko@suse.com>
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>

Someone has an 86 column display.
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Andrew stated the following

	We have quite a history of remote parts of the kernel using
	weird/wrong/inexplicable combinations of __GFP_ flags.	I tend
	to think that this is because we didn't adequately explain the
	interface.

	And I don't think that gfp.h really improved much in this area as
	a result of this patchset.  Could you go through it some time and
	decide if we've adequately documented all this stuff?

This patches first moves some GFP flag combinations that are part of the MM
internals to mm/internal.h. The rest of the patch documents the __GFP_FOO
bits under various headings and then documents the flag combinations. It
will not help callers that are brain damaged but the clarity might motivate
some fixes and avoid future mistakes.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vitaly Wool <vitalywool@gmail.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>

The primary purpose of watermarks is to ensure that reclaim can always
make forward progress in PF_MEMALLOC context (kswapd and direct reclaim).
These assume that order-0 allocations are all that is necessary for
forward progress.

High-order watermarks serve a different purpose.  Kswapd had no high-order
awareness before they were introduced
(https://lkml.kernel.org/r/413AA7B2.4000907@yahoo.com.au).  This was
particularly important when there were high-order atomic requests.  The
watermarks both gave kswapd awareness and made a reserve for those atomic
requests.

There are two important side-effects of this.  The most important is that
a non-atomic high-order request can fail even though free pages are
available and the order-0 watermarks are ok.  The second is that
high-order watermark checks are expensive as the free list counts up to
the requested order must be examined.

With the introduction of MIGRATE_HIGHATOMIC it is no longer necessary to
have high-order watermarks.  Kswapd and compaction still need high-order
awareness which is handled by checking that at least one suitable
high-order page is free.

With the patch applied, there was little difference in the allocation
failure rates as the atomic reserves are small relative to the number of
allocation attempts.  The expected impact is that there will never be an
allocation failure report that shows suitable pages on the free lists.

The one potential side-effect of this is that in a vanilla kernel, the
watermark checks may have kept a free page for an atomic allocation.  Now,
we are 100% relying on the HighAtomic reserves and an early allocation to
have allocated them.  If the first high-order atomic allocation is after
the system is already heavily fragmented then it'll fail.

[akpm@linux-foundation.org: simplify __zone_watermark_ok(), per Vlastimil]
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@gmail.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>

High-order watermark checking exists for two reasons -- kswapd high-order
awareness and protection for high-order atomic requests.  Historically the
kernel depended on MIGRATE_RESERVE to preserve min_free_kbytes as
high-order free pages for as long as possible.  This patch introduces
MIGRATE_HIGHATOMIC that reserves pageblocks for high-order atomic
allocations on demand and avoids using those blocks for order-0
allocations.  This is more flexible and reliable than MIGRATE_RESERVE was.

A MIGRATE_HIGHORDER pageblock is created when an atomic high-order
allocation request steals a pageblock but limits the total number to 1% of
the zone.  Callers that speculatively abuse atomic allocations for
long-lived high-order allocations to access the reserve will quickly fail.
 Note that SLUB is currently not such an abuser as it reclaims at least
once.  It is possible that the pageblock stolen has few suitable
high-order pages and will need to steal again in the near future but there
would need to be strong justification to search all pageblocks for an
ideal candidate.

The pageblocks are unreserved if an allocation fails after a direct
reclaim attempt.

The watermark checks account for the reserved pageblocks when the
allocation request is not a high-order atomic allocation.

The reserved pageblocks can not be used for order-0 allocations.  This may
allow temporary wastage until a failed reclaim reassigns the pageblock.
This is deliberate as the intent of the reservation is to satisfy a
limited number of atomic high-order short-lived requests if the system
requires them.

The stutter benchmark was used to evaluate this but while it was running
there was a systemtap script that randomly allocated between 1 high-order
page and 12.5% of memory's worth of order-3 pages using GFP_ATOMIC.  This
is much larger than the potential reserve and it does not attempt to be
realistic.  It is intended to stress random high-order allocations from an
unknown source, show that there is a reduction in failures without
introducing an anomaly where atomic allocations are more reliable than
regular allocations.  The amount of memory reserved varied throughout the
workload as reserves were created and reclaimed under memory pressure.
The allocation failures once the workload warmed up were as follows;

4.2-rc5-vanilla		70%
4.2-rc5-atomic-reserve	56%

The failure rate was also measured while building multiple kernels.  The
failure rate was 14% but is 6% with this patch applied.

Overall, this is a small reduction but the reserves are small relative to
the number of allocation requests.  In early versions of the patch, the
failure rate reduced by a much larger amount but that required much larger
reserves and perversely made atomic allocations seem more reliable than
regular allocations.

[yalin.wang2010@gmail.com: fix redundant check and a memory leak]
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Nyalin wang <yalin.wang2010@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

MIGRATE_RESERVE preserves an old property of the buddy allocator that
existed prior to fragmentation avoidance -- min_free_kbytes worth of pages
tended to remain contiguous until the only alternative was to fail the
allocation.  At the time it was discovered that high-order atomic
allocations relied on this property so MIGRATE_RESERVE was introduced.  A
later patch will introduce an alternative MIGRATE_HIGHATOMIC so this patch
deletes MIGRATE_RESERVE and supporting code so it'll be easier to review.
Note that this patch in isolation may look like a false regression if
someone was bisecting high-order atomic allocation failures.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vitaly Wool <vitalywool@gmail.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>

The zonelist cache (zlc) was introduced to skip over zones that were
recently known to be full.  This avoided expensive operations such as the
cpuset checks, watermark calculations and zone_reclaim.  The situation
today is different and the complexity of zlc is harder to justify.

1) The cpuset checks are no-ops unless a cpuset is active and in general
   are a lot cheaper.

2) zone_reclaim is now disabled by default and I suspect that was a large
   source of the cost that zlc wanted to avoid. When it is enabled, it's
   known to be a major source of stalling when nodes fill up and it's
   unwise to hit every other user with the overhead.

3) Watermark checks are expensive to calculate for high-order
   allocation requests. Later patches in this series will reduce the cost
   of the watermark checking.

4) The most important issue is that in the current implementation it
   is possible for a failed THP allocation to mark a zone full for order-0
   allocations and cause a fallback to remote nodes.

The last issue could be addressed with additional complexity but as the
benefit of zlc is questionable, it is better to remove it.  If stalls due
to zone_reclaim are ever reported then an alternative would be to
introduce deferring logic based on a timeout inside zone_reclaim itself
and leave the page allocator fast paths alone.

The impact on page-allocator microbenchmarks is negligible as they don't
hit the paths where the zlc comes into play.  Most page-reclaim related
workloads showed no noticeable difference as a result of the removal.

The impact was noticeable in a workload called "stutter".  One part uses a
lot of anonymous memory, a second measures mmap latency and a third copies
a large file.  In an ideal world the latency application would not notice
the mmap latency.  On a 2-node machine the results of this patch are

stutter
                             4.3.0-rc1             4.3.0-rc1
                              baseline              nozlc-v4
Min         mmap     20.9243 (  0.00%)     20.7716 (  0.73%)
1st-qrtle   mmap     22.0612 (  0.00%)     22.0680 ( -0.03%)
2nd-qrtle   mmap     22.3291 (  0.00%)     22.3809 ( -0.23%)
3rd-qrtle   mmap     25.2244 (  0.00%)     25.2396 ( -0.06%)
Max-90%     mmap     48.0995 (  0.00%)     28.3713 ( 41.02%)
Max-93%     mmap     52.5557 (  0.00%)     36.0170 ( 31.47%)
Max-95%     mmap     55.8173 (  0.00%)     47.3163 ( 15.23%)
Max-99%     mmap     67.3781 (  0.00%)     70.1140 ( -4.06%)
Max         mmap  24447.6375 (  0.00%)  12915.1356 ( 47.17%)
Mean        mmap     33.7883 (  0.00%)     27.7944 ( 17.74%)
Best99%Mean mmap     27.7825 (  0.00%)     25.2767 (  9.02%)
Best95%Mean mmap     26.3912 (  0.00%)     23.7994 (  9.82%)
Best90%Mean mmap     24.9886 (  0.00%)     23.2251 (  7.06%)
Best50%Mean mmap     22.0157 (  0.00%)     22.0261 ( -0.05%)
Best10%Mean mmap     21.6705 (  0.00%)     21.6083 (  0.29%)
Best5%Mean  mmap     21.5581 (  0.00%)     21.4611 (  0.45%)
Best1%Mean  mmap     21.3079 (  0.00%)     21.1631 (  0.68%)

Note that the maximum stall latency went from 24 seconds to 12 which is
still bad but an improvement.  The milage varies considerably 2-node
machine on an earlier test went from 494 seconds to 47 seconds and a
4-node machine that tested an earlier version of this patch went from a
worst case stall time of 6 seconds to 67ms.  The nature of the benchmark
is inherently unpredictable as it is hammering the system and the milage
will vary between machines.

There is a secondary impact with potentially more direct reclaim because
zones are now being considered instead of being skipped by zlc.  In this
particular test run it did not occur so will not be described.  However,
in at least one test the following was observed

1. Direct reclaim rates were higher. This was likely due to direct reclaim
  being entered instead of the zlc disabling a zone and busy looping.
  Busy looping may have the effect of allowing kswapd to make more
  progress and in some cases may be better overall. If this is found then
  the correct action is to put direct reclaimers to sleep on a waitqueue
  and allow kswapd make forward progress. Busy looping on the zlc is even
  worse than when the allocator used to blindly call congestion_wait().

2. There was higher swap activity as direct reclaim was active.

3. Direct reclaim efficiency was lower. This is related to 1 as more
  scanning activity also encountered more pages that could not be
  immediately reclaimed

In that case, the direct page scan and reclaim rates are noticeable but
it is not considered a problem for a few reasons

1. The test is primarily concerned with latency. The mmap attempts are also
   faulted which means there are THP allocation requests. The ZLC could
   cause zones to be disabled causing the process to busy loop instead
   of reclaiming.  This looks like elevated direct reclaim activity but
   it's the correct action to take based on what processes requested.

2. The test hammers reclaim and compaction heavily. The number of successful
   THP faults is highly variable but affects the reclaim stats. It's not a
   realistic or reasonable measure of page reclaim activity.

3. No other page-reclaim intensive workload that was tested showed a problem.

4. If a workload is identified that benefitted from the busy looping then it
   should be fixed by having direct reclaimers sleep on a wait queue until
   woken by kswapd instead of busy looping. We had this class of problem before
   when congestion_waits() with a fixed timeout was a brain damaged decision
   but happened to benefit some workloads.

If a workload is identified that relied on the zlc to busy loop then it
should be fixed correctly and have a direct reclaimer sleep on a waitqueue
until woken by kswapd.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NChristoph Lameter <cl@linux.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Vitaly Wool <vitalywool@gmail.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>

__GFP_WAIT was used to signal that the caller was in atomic context and
could not sleep.  Now it is possible to distinguish between true atomic
context and callers that are not willing to sleep.  The latter should
clear __GFP_DIRECT_RECLAIM so kswapd will still wake.  As clearing
__GFP_WAIT behaves differently, there is a risk that people will clear the
wrong flags.  This patch renames __GFP_WAIT to __GFP_RECLAIM to clearly
indicate what it does -- setting it allows all reclaim activity, clearing
them prevents it.

[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@gmail.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>

GFP_IOFS was intended to be shorthand for clearing two flags, not a set of
allocation flags.  There is only one user of this flag combination now and
there appears to be no reason why Lustre had to be protected from reclaim
stalls.  As none of the sites appear to be atomic, this patch simply
deletes GFP_IOFS and converts Lustre to using GFP_KERNEL, GFP_NOFS or
GFP_NOIO as appropriate.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Cc: Oleg Drokin <oleg.drokin@intel.com>
Cc: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd

__GFP_WAIT has been used to identify atomic context in callers that hold
spinlocks or are in interrupts.  They are expected to be high priority and
have access one of two watermarks lower than "min" which can be referred
to as the "atomic reserve".  __GFP_HIGH users get access to the first
lower watermark and can be called the "high priority reserve".

Over time, callers had a requirement to not block when fallback options
were available.  Some have abused __GFP_WAIT leading to a situation where
an optimisitic allocation with a fallback option can access atomic
reserves.

This patch uses __GFP_ATOMIC to identify callers that are truely atomic,
cannot sleep and have no alternative.  High priority users continue to use
__GFP_HIGH.  __GFP_DIRECT_RECLAIM identifies callers that can sleep and
are willing to enter direct reclaim.  __GFP_KSWAPD_RECLAIM to identify
callers that want to wake kswapd for background reclaim.  __GFP_WAIT is
redefined as a caller that is willing to enter direct reclaim and wake
kswapd for background reclaim.

This patch then converts a number of sites

o __GFP_ATOMIC is used by callers that are high priority and have memory
  pools for those requests. GFP_ATOMIC uses this flag.

o Callers that have a limited mempool to guarantee forward progress clear
  __GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall
  into this category where kswapd will still be woken but atomic reserves
  are not used as there is a one-entry mempool to guarantee progress.

o Callers that are checking if they are non-blocking should use the
  helper gfpflags_allow_blocking() where possible. This is because
  checking for __GFP_WAIT as was done historically now can trigger false
  positives. Some exceptions like dm-crypt.c exist where the code intent
  is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to
  flag manipulations.

o Callers that built their own GFP flags instead of starting with GFP_KERNEL
  and friends now also need to specify __GFP_KSWAPD_RECLAIM.

The first key hazard to watch out for is callers that removed __GFP_WAIT
and was depending on access to atomic reserves for inconspicuous reasons.
In some cases it may be appropriate for them to use __GFP_HIGH.

The second key hazard is callers that assembled their own combination of
GFP flags instead of starting with something like GFP_KERNEL.  They may
now wish to specify __GFP_KSWAPD_RECLAIM.  It's almost certainly harmless
if it's missed in most cases as other activity will wake kswapd.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@gmail.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>

This patch redefines which GFP bits are used for specifying mobility and
the order of the migrate types.  Once redefined it's possible to convert
GFP flags to a migrate type with a simple mask and shift.  The only
downside is that readers of OOM kill messages and allocation failures may
have been used to the existing values but scripts/gfp-translate will help.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vitaly Wool <vitalywool@gmail.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>

There is a seqcounter that protects against spurious allocation failures
when a task is changing the allowed nodes in a cpuset.  There is no need
to check the seqcounter until a cpuset exists.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NChristoph Lameter <cl@linux.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Vitaly Wool <vitalywool@gmail.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>

File-backed pages that will be immediately written are balanced between
zones.  This heuristic tries to avoid having a single zone filled with
recently dirtied pages but the checks are unnecessarily expensive.  Move
consider_zone_balanced into the alloc_context instead of checking bitmaps
multiple times.  The patch also gives the parameter a more meaningful
name.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Vitaly Wool <vitalywool@gmail.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>

Overall, the intent of this series is to remove the zonelist cache which
was introduced to avoid high overhead in the page allocator.  Once this is
done, it is necessary to reduce the cost of watermark checks.

The series starts with minor micro-optimisations.

Next it notes that GFP flags that affect watermark checks are abused.
__GFP_WAIT historically identified callers that could not sleep and could
access reserves.  This was later abused to identify callers that simply
prefer to avoid sleeping and have other options.  A patch distinguishes
between atomic callers, high-priority callers and those that simply wish
to avoid sleep.

The zonelist cache has been around for a long time but it is of dubious
merit with a lot of complexity and some issues that are explained.  The
most important issue is that a failed THP allocation can cause a zone to
be treated as "full".  This potentially causes unnecessary stalls, reclaim
activity or remote fallbacks.  The issues could be fixed but it's not
worth it.  The series places a small number of other micro-optimisations
on top before examining GFP flags watermarks.

High-order watermarks enforcement can cause high-order allocations to fail
even though pages are free.  The watermark checks both protect high-order
atomic allocations and make kswapd aware of high-order pages but there is
a much better way that can be handled using migrate types.  This series
uses page grouping by mobility to reserve pageblocks for high-order
allocations with the size of the reservation depending on demand.  kswapd
awareness is maintained by examining the free lists.  By patch 12 in this
series, there are no high-order watermark checks while preserving the
properties that motivated the introduction of the watermark checks.

This patch (of 10):

No user of zone_watermark_ok_safe() specifies alloc_flags.  This patch
removes the unnecessary parameter.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NChristoph Lameter <cl@linux.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Introduce is_sysrq_oom helper function indicating oom kill triggered
by sysrq to improve readability.

No functional changes.
Signed-off-by: NYaowei Bai <bywxiaobai@163.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Pull backlight updates from Lee Jones:
 "New Device Support
   - None

  New Functionality:
   - None

  Core Frameworks:
   - Reject legacy PWM request for device defined in DT

  Fix-ups:
   - Remove unnecessary MODULE_ALIAS(); adp8860_bl, adp8870_bl
   - Simplify code: pm8941-wled
   - Supply default-brightness logic; pm8941-wled

  Bug Fixes:
   - Clean up OF node; 88pm860x_bl
   - Ensure struct is zeroed; lp855x_bl"

* tag 'backlight-for-linus-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/backlight:
  backlight: pm8941-wled: Add default-brightness property
  backlight: pm8941-wled: Fix ptr_ret.cocci warnings
  backlight: pwm: Reject legacy PWM request for device defined in DT
  backlight: 88pm860x_bl: Add missing of_node_put
  backlight: adp8870: Remove unnecessary MODULE_ALIAS()
  backlight: adp8860: Remove unnecessary MODULE_ALIAS()
  backlight: lp855x: Make sure props struct is zeroed

Commit b158b69a ("mfd: rtsx: Simplify function return logic")
removed the use of the 'err' variable, but left the variable itself
around, resulting in gcc quite reasonably warning:

    drivers/mfd/rtsx_pcr.c: In function ‘rtsx_pci_set_pull_ctl’:
    drivers/mfd/rtsx_pcr.c:565:6: warning: unused variable ‘err’ [-Wunused-variable]
      int err;
          ^

Get rid of the unused variable, and avoid the new warning.

Cc: Javier Martinez Canillas <javier@osg.samsung.com>
Cc: Lee Jones <lee.jones@linaro.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Pull MFD updates from Lee Jones:
 "New Device Support:
   - Add support for 88pm860; 88pm80x
   - Add support for 24c08 EEPROM; at24
   - Add support for Broxton Whiskey Cove; intel*
   - Add support for RTS522A; rts5227
   - Add support for I2C devices; intel_quark_i2c_gpio

  New Functionality:
   - Add microphone support; arizona
   - Add general purpose switch support; arizona
   - Add fuel-gauge support; da9150-core
   - Add shutdown support; sec-core
   - Add charger support; tps65217
   - Add flexible serial communication unit support; atmel-flexcom
   - Add power button support; axp20x
   - Add led-flash support; rt5033

  Core Frameworks:
   - Supply a generic macro for defining Regmap IRQs
   - Rework ACPI child device matching

  Fix-ups:
   - Use Regmap to access registers; tps6105x
   - Use DEFINE_RES_IRQ_NAMED() macro; da9150
   - Re-arrange device registration order; intel_quark_i2c_gpio
   - Allow OF matching; cros_ec_i2c, atmel-hlcdc, hi6421-pmic, max8997, sm501
   - Handle deferred probe; twl6040
   - Improve accuracy of headphone detect; arizona
   - Unnecessary MODULE_ALIAS() removal; bcm590xx, rt5033
   - Remove unused code; htc-i2cpld, arizona, pcf50633-irq, sec-core
   - Simplify code; kempld, rts5209, da903x, lm3533, da9052, arizona
   - Remove #iffery; arizona
   - DT binding adaptions; many

  Bug Fixes:
   - Fix possible NULL pointer dereference; wm831x, tps6105x
   - Fix 64bit bug; intel_soc_pmic_bxtwc
   - Fix signedness issue; arizona"

* tag 'mfd-for-linus-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd: (73 commits)
  bindings: mfd: s2mps11: Add documentation for s2mps15 PMIC
  mfd: sec-core: Remove unused s2mpu02-rtc and s2mpu02-clk children
  extcon: arizona: Add extcon specific device tree binding document
  MAINTAINERS: Add binding docs for Cirrus Logic/Wolfson Arizona devices
  mfd: arizona: Remove bindings covered in new subsystem specific docs
  mfd: rt5033: Add RT5033 Flash led sub device
  mfd: lpss: Add Intel Broxton PCI IDs
  mfd: lpss: Add Broxton ACPI IDs
  mfd: arizona: Signedness bug in arizona_runtime_suspend()
  mfd: axp20x: Add a cell for the power button part of the, axp288 PMICs
  mfd: dt-bindings: Document pulled down WRSTBI pin on S2MPS1X
  mfd: sec-core: Disable buck voltage reset on watchdog falling edge
  mfd: sec-core: Dump PMIC revision to find out the HW
  mfd: arizona: Use correct type ID for device tree config
  mfd: arizona: Remove use of codec build config #ifdefs
  mfd: arizona: Simplify adding subdevices
  mfd: arizona: Downgrade type mismatch messages to dev_warn
  mfd: arizona: Factor out checking of jack detection state
  mfd: arizona: Factor out DCVDD isolation control
  mfd: Make TPS6105X select REGMAP_I2C
  ...

It turns out that we still have issues with the EFI memory map that ends
up polluting our kernel page tables with writable executable pages.

That will get sorted out, but in the meantime let's not make the scary
complaint about them be on by default.  The code is useful for
developers, but not ready for end user testing yet.
Acked-by: NBorislav Petkov <bp@alien8.de>
Acked-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>