linux-stable.git/include/linux/swap.h, branch v4.2.1

suspend: simplify block I/O handling

2015-05-19T15:19:59+00:00

Stop abusing struct page functionality and the swap end_io handler, and
instead add a modified version of the blk-lib.c bio_batch helpers.

Also move the block I/O code into swap.c as they are directly tied into
each other.

Signed-off-by: Christoph Hellwig 
Tested-by: Pavel Machek 
Tested-by: Ming Lin 
Acked-by: Pavel Machek 
Acked-by: Rafael J. Wysocki 
Signed-off-by: Jens Axboe

mm: rename deactivate_page to deactivate_file_page

2015-04-15T23:35:17+00:00

"deactivate_page" was created for file invalidation so it has too
specific logic for file-backed pages.  So, let's change the name of the
function and date to a file-specific one and yield the generic name.

Signed-off-by: Minchan Kim 
Cc: Michal Hocko 
Cc: Johannes Weiner 
Cc: Mel Gorman 
Cc: Rik van Riel 
Cc: Shaohua Li 
Cc: Wang, Yalin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

swap: remove unused mem_cgroup_uncharge_swapcache declaration

2015-02-12T01:06:00+00:00

The body of this function was removed by commit 0a31bc97c80c ("mm:
memcontrol: rewrite uncharge API").

Signed-off-by: Vladimir Davydov 
Acked-by: Michal Hocko 
Acked-by: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: move swp_entry_t definition to include/linux/mm_types.h

2014-12-13T20:42:47+00:00

swp_entry_t being defined in include/linux/swap.h instead of
include/linux/mm_types.h causes cyclic include dependency later when
include/linux/page_cgroup.h is included from writeback path.  Move the
definition to include/linux/mm_types.h.

While at it, reformat the comment above it.

Signed-off-by: Tejun Heo 
Cc: Mel Gorman 
Cc: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: memcontrol: fix transparent huge page allocations under pressure

2014-10-10T02:25:59+00:00

In a memcg with even just moderate cache pressure, success rates for
transparent huge page allocations drop to zero, wasting a lot of effort
that the allocator puts into assembling these pages.

The reason for this is that the memcg reclaim code was never designed for
higher-order charges.  It reclaims in small batches until there is room
for at least one page.  Huge page charges only succeed when these batches
add up over a series of huge faults, which is unlikely under any
significant load involving order-0 allocations in the group.

Remove that loop on the memcg side in favor of passing the actual reclaim
goal to direct reclaim, which is already set up and optimized to meet
higher-order goals efficiently.

This brings memcg's THP policy in line with the system policy: if the
allocator painstakingly assembles a hugepage, memcg will at least make an
honest effort to charge it.  As a result, transparent hugepage allocation
rates amid cache activity are drastically improved:

                                      vanilla                 patched
pgalloc                 4717530.80 (  +0.00%)   4451376.40 (  -5.64%)
pgfault                  491370.60 (  +0.00%)    225477.40 ( -54.11%)
pgmajfault                    2.00 (  +0.00%)         1.80 (  -6.67%)
thp_fault_alloc               0.00 (  +0.00%)       531.60 (+100.00%)
thp_fault_fallback          749.00 (  +0.00%)       217.40 ( -70.88%)

[ Note: this may in turn increase memory consumption from internal
  fragmentation, which is an inherent risk of transparent hugepages.
  Some setups may have to adjust the memcg limits accordingly to
  accomodate this - or, if the machine is already packed to capacity,
  disable the transparent huge page feature. ]

Signed-off-by: Johannes Weiner 
Reviewed-by: Vladimir Davydov 
Cc: Michal Hocko 
Cc: Dave Hansen 
Cc: Greg Thelen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: remove noisy remainder of the scan_unevictable interface

2014-10-10T02:25:55+00:00

The deprecation warnings for the scan_unevictable interface triggers by
scripts doing `sysctl -a | grep something else'.  This is annoying and not
helpful.

The interface has been defunct since 264e56d8247e ("mm: disable user
interface to manually rescue unevictable pages"), which was in 2011, and
there haven't been any reports of usecases for it, only reports that the
deprecation warnings are annying.  It's unlikely that anybody is using
this interface specifically at this point, so remove it.

Signed-off-by: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: memcontrol: rewrite uncharge API

2014-08-08T22:57:17+00:00

The memcg uncharging code that is involved towards the end of a page's
lifetime - truncation, reclaim, swapout, migration - is impressively
complicated and fragile.

Because anonymous and file pages were always charged before they had their
page->mapping established, uncharges had to happen when the page type
could still be known from the context; as in unmap for anonymous, page
cache removal for file and shmem pages, and swap cache truncation for swap
pages.  However, these operations happen well before the page is actually
freed, and so a lot of synchronization is necessary:

- Charging, uncharging, page migration, and charge migration all need
  to take a per-page bit spinlock as they could race with uncharging.

- Swap cache truncation happens during both swap-in and swap-out, and
  possibly repeatedly before the page is actually freed.  This means
  that the memcg swapout code is called from many contexts that make
  no sense and it has to figure out the direction from page state to
  make sure memory and memory+swap are always correctly charged.

- On page migration, the old page might be unmapped but then reused,
  so memcg code has to prevent untimely uncharging in that case.
  Because this code - which should be a simple charge transfer - is so
  special-cased, it is not reusable for replace_page_cache().

But now that charged pages always have a page->mapping, introduce
mem_cgroup_uncharge(), which is called after the final put_page(), when we
know for sure that nobody is looking at the page anymore.

For page migration, introduce mem_cgroup_migrate(), which is called after
the migration is successful and the new page is fully rmapped.  Because
the old page is no longer uncharged after migration, prevent double
charges by decoupling the page's memcg association (PCG_USED and
pc->mem_cgroup) from the page holding an actual charge.  The new bits
PCG_MEM and PCG_MEMSW represent the respective charges and are transferred
to the new page during migration.

mem_cgroup_migrate() is suitable for replace_page_cache() as well,
which gets rid of mem_cgroup_replace_page_cache().  However, care
needs to be taken because both the source and the target page can
already be charged and on the LRU when fuse is splicing: grab the page
lock on the charge moving side to prevent changing pc->mem_cgroup of a
page under migration.  Also, the lruvecs of both pages change as we
uncharge the old and charge the new during migration, and putback may
race with us, so grab the lru lock and isolate the pages iff on LRU to
prevent races and ensure the pages are on the right lruvec afterward.

Swap accounting is massively simplified: because the page is no longer
uncharged as early as swap cache deletion, a new mem_cgroup_swapout() can
transfer the page's memory+swap charge (PCG_MEMSW) to the swap entry
before the final put_page() in page reclaim.

Finally, page_cgroup changes are now protected by whatever protection the
page itself offers: anonymous pages are charged under the page table lock,
whereas page cache insertions, swapin, and migration hold the page lock.
Uncharging happens under full exclusion with no outstanding references.
Charging and uncharging also ensure that the page is off-LRU, which
serializes against charge migration.  Remove the very costly page_cgroup
lock and set pc->flags non-atomically.

[mhocko@suse.cz: mem_cgroup_charge_statistics needs preempt_disable]
[vdavydov@parallels.com: fix flags definition]
Signed-off-by: Johannes Weiner 
Cc: Hugh Dickins 
Cc: Tejun Heo 
Cc: Vladimir Davydov 
Tested-by: Jet Chen 
Acked-by: Michal Hocko 
Tested-by: Felipe Balbi 
Signed-off-by: Vladimir Davydov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: memcontrol: rewrite charge API

2014-08-08T22:57:17+00:00

These patches rework memcg charge lifetime to integrate more naturally
with the lifetime of user pages.  This drastically simplifies the code and
reduces charging and uncharging overhead.  The most expensive part of
charging and uncharging is the page_cgroup bit spinlock, which is removed
entirely after this series.

Here are the top-10 profile entries of a stress test that reads a 128G
sparse file on a freshly booted box, without even a dedicated cgroup (i.e.
 executing in the root memcg).  Before:

    15.36%              cat  [kernel.kallsyms]   [k] copy_user_generic_string
    13.31%              cat  [kernel.kallsyms]   [k] memset
    11.48%              cat  [kernel.kallsyms]   [k] do_mpage_readpage
     4.23%              cat  [kernel.kallsyms]   [k] get_page_from_freelist
     2.38%              cat  [kernel.kallsyms]   [k] put_page
     2.32%              cat  [kernel.kallsyms]   [k] __mem_cgroup_commit_charge
     2.18%          kswapd0  [kernel.kallsyms]   [k] __mem_cgroup_uncharge_common
     1.92%          kswapd0  [kernel.kallsyms]   [k] shrink_page_list
     1.86%              cat  [kernel.kallsyms]   [k] __radix_tree_lookup
     1.62%              cat  [kernel.kallsyms]   [k] __pagevec_lru_add_fn

After:

    15.67%           cat  [kernel.kallsyms]   [k] copy_user_generic_string
    13.48%           cat  [kernel.kallsyms]   [k] memset
    11.42%           cat  [kernel.kallsyms]   [k] do_mpage_readpage
     3.98%           cat  [kernel.kallsyms]   [k] get_page_from_freelist
     2.46%           cat  [kernel.kallsyms]   [k] put_page
     2.13%       kswapd0  [kernel.kallsyms]   [k] shrink_page_list
     1.88%           cat  [kernel.kallsyms]   [k] __radix_tree_lookup
     1.67%           cat  [kernel.kallsyms]   [k] __pagevec_lru_add_fn
     1.39%       kswapd0  [kernel.kallsyms]   [k] free_pcppages_bulk
     1.30%           cat  [kernel.kallsyms]   [k] kfree

As you can see, the memcg footprint has shrunk quite a bit.

   text    data     bss     dec     hex filename
  37970    9892     400   48262    bc86 mm/memcontrol.o.old
  35239    9892     400   45531    b1db mm/memcontrol.o

This patch (of 4):

The memcg charge API charges pages before they are rmapped - i.e.  have an
actual "type" - and so every callsite needs its own set of charge and
uncharge functions to know what type is being operated on.  Worse,
uncharge has to happen from a context that is still type-specific, rather
than at the end of the page's lifetime with exclusive access, and so
requires a lot of synchronization.

Rewrite the charge API to provide a generic set of try_charge(),
commit_charge() and cancel_charge() transaction operations, much like
what's currently done for swap-in:

  mem_cgroup_try_charge() attempts to reserve a charge, reclaiming
  pages from the memcg if necessary.

  mem_cgroup_commit_charge() commits the page to the charge once it
  has a valid page->mapping and PageAnon() reliably tells the type.

  mem_cgroup_cancel_charge() aborts the transaction.

This reduces the charge API and enables subsequent patches to
drastically simplify uncharging.

As pages need to be committed after rmap is established but before they
are added to the LRU, page_add_new_anon_rmap() must stop doing LRU
additions again.  Revive lru_cache_add_active_or_unevictable().

[hughd@google.com: fix shmem_unuse]
[hughd@google.com: Add comments on the private use of -EAGAIN]
Signed-off-by: Johannes Weiner 
Acked-by: Michal Hocko 
Cc: Tejun Heo 
Cc: Vladimir Davydov 
Signed-off-by: Hugh Dickins 
Cc: Naoya Horiguchi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: replace init_page_accessed by __SetPageReferenced

2014-08-07T01:01:19+00:00

Do we really need an exported alias for __SetPageReferenced()? Its
callers better know what they're doing, in which case the page would not
be already marked referenced.  Kill init_page_accessed(), just
__SetPageReferenced() inline.

Signed-off-by: Hugh Dickins 
Acked-by: Mel Gorman 
Cc: Johannes Weiner 
Cc: Vlastimil Babka 
Cc: Michal Hocko 
Cc: Dave Hansen 
Cc: Prabhakar Lad 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/vmscan.c: use DIV_ROUND_UP for calculation of zone's balance_gap and correct comments.

2014-06-04T23:54:11+00:00

Currently, we use (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1)
/ KSWAPD_ZONE_BALANCE_GAP_RATIO to avoid a zero gap value.  It's better to
use DIV_ROUND_UP macro for neater code and clear meaning.

Besides, the gap value is calculated against the per-zone "managed pages",
not "present pages".  This patch also corrects the comment and do some
rephrasing.

Signed-off-by: Jianyu Zhan 
Acked-by: Rik van Riel 
Acked-by: Rafael Aquini 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds