We observed failures in the 'memcontrol02' test case from the Linux Test Project (LTP) [1] when running on a 256-core server with the 6.6.y kernel. The test fails due to stale memory.stat values being returned, which is caused by the current stats flushing implementation's limitations with large core counts.
This series backports the memcg subtree stats flushing improvements from Linux 6.8 to 6.6.y to address the issue. The main goal is to restore per-memcg stats flushing with dynamic thresholds, which improves both accuracy and performance of memory cgroup statistics, especially on high-core-count systems.
Background ==========
The current stats flushing in 6.6.y flushes the entire memcg hierarchy with a global threshold. This is not efficient and can cause stale stats when read 'memory.stat'.
Dependency Patches ==================
Patches 1-2 are dependencies required for clean application of the main series:
Patch 1: 811244a501b9 "mm: memcg: add THP swap out info for anonymous reclaim"
This patch adds THP_SWPOUT and THP_SWPOUT_FALLBACK entries to the memcg_vm_event_stat[] array. It is needed because patch 4 (e0bf1dc859fd) moves the vmstats struct definitions, including this array. Without this patch, the array structure would not match between 6.6.y and 6.8, causing context conflicts during cherry-pick.
The patch is already in mainline (merged in v6.7) but was not included in the stable 6.6.y branch.
Patch 2: 7108cc3f765c "mm: memcg: add per-memcg zswap writeback stat"
This patch adds the ZSWPWB entry to the memcg_vm_event_stat[] array. Like patch 1, it is required for patch 4 to apply cleanly. The array structure must match the 6.8 state for the code movement to succeed without conflicts.
This patch is also in mainline (merged in v6.8) but was not backported to 6.6.y.
Main Series ===========
Patches 3-7 are the core memcg stats flushing improvements:
- Patch 3: Renames flush_next_time to flush_last_time for clarity - Patch 4: Moves vmstats struct definitions for better code organization - Patch 5: Implements per-memcg stats flushing thresholds (key change) - Patch 6: Moves stats flush into workingset_test_recent() - Patch 7: Restores subtree stats flushing (main feature)
Cherry-Pick Notes for Patch 7 ==============================
Patch 7 (7d7ef0a4686a) requires manual conflict resolution in mm/zswap.c:
The conflict occurs because this patch includes changes to zswap shrinker code that was introduced in Linux 6.8. Since this new shrinker infrastructure does not exist in 6.6.y, the conflicting code should be removed during cherry-pick.
Resolution: Keep the 6.6.y (HEAD) version of mm/zswap.c and discard the new shrinker code from the patch. The conflict markers will show:
<<<<<<< HEAD // existing 6.6.y code ======= // new 6.8 shrinker code (shrink_memcg_cb, zswap_shrinker_scan, etc.)
> 7d7ef0a4686a
Simply keep the HEAD version and remove everything between the "=======" and ">>>>>>>" markers. This is safe because the zswap shrinker is a separate new feature, not a dependency for the memcg stats changes.
Additionally, if you encounter a conflict in mm/workingset.c, it may be due to commit 417dbd7be383 ("mm: ratelimit stat flush from workingset shrinker") which was backported to 6.6.y. The resolution is to use: mem_cgroup_flush_stats_ratelimited(sc->memcg) which preserves the performance optimization while using the new API.
Testing =======
This series has been extensively tested upstream with: - 5000 concurrent workers in 500 cgroups doing allocations and reclaim - 250k threads reading stats every 100ms in 50k cgroups - No performance regressions observed with per-memcg thresholds
The changes improve both stats accuracy and reduce unnecessary flushing overhead.
References ==========
[1] Linux Test Project (LTP): https://github.com/linux-test-project/ltp
Domenico Cerasuolo (1): mm: memcg: add per-memcg zswap writeback stat
Xin Hao (1): mm: memcg: add THP swap out info for anonymous reclaim
Yosry Ahmed (5): mm: memcg: change flush_next_time to flush_last_time mm: memcg: move vmstats structs definition above flushing code mm: memcg: make stats flushing threshold per-memcg mm: workingset: move the stats flush into workingset_test_recent() mm: memcg: restore subtree stats flushing
Documentation/admin-guide/cgroup-v2.rst | 9 + include/linux/memcontrol.h | 8 +- include/linux/vm_event_item.h | 1 + mm/memcontrol.c | 266 +++++++++++++----------- mm/page_io.c | 8 +- mm/vmscan.c | 3 +- mm/vmstat.c | 1 + mm/workingset.c | 42 ++-- mm/zswap.c | 4 + 9 files changed, 203 insertions(+), 139 deletions(-)
-- 2.50.1
From: Xin Hao vernhao@tencent.com
[ Upstream commit 811244a501b967b00fecb1ae906d5dc6329c91e0 ]
At present, we support per-memcg reclaim strategy, however we do not know the number of transparent huge pages being reclaimed, as we know the transparent huge pages need to be splited before reclaim them, and they will bring some performance bottleneck effect. for example, when two memcg (A & B) are doing reclaim for anonymous pages at same time, and 'A' memcg is reclaiming a large number of transparent huge pages, we can better analyze that the performance bottleneck will be caused by 'A' memcg. therefore, in order to better analyze such problems, there add THP swap out info for per-memcg.
[akpm@linux-foundation.orgL fix swap_writepage_fs(), per Johannes] Link: https://lkml.kernel.org/r/20230913213343.GB48476@cmpxchg.org Link: https://lkml.kernel.org/r/20230913164938.16918-1-vernhao@tencent.com Signed-off-by: Xin Hao vernhao@tencent.com Suggested-by: Johannes Weiner hannes@cmpxchg.org Acked-by: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@suse.com Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Shakeel Butt shakeelb@google.com Cc: Muchun Song songmuchun@bytedance.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Leon Huang Fu leon.huangfu@shopee.com --- Documentation/admin-guide/cgroup-v2.rst | 9 +++++++++ mm/memcontrol.c | 2 ++ mm/page_io.c | 8 ++++---- mm/vmscan.c | 1 + 4 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index b26b5274eaaf..622a7f28db1f 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -1532,6 +1532,15 @@ PAGE_SIZE multiple when read back. collapsing an existing range of pages. This counter is not present when CONFIG_TRANSPARENT_HUGEPAGE is not set.
+ thp_swpout (npn) + Number of transparent hugepages which are swapout in one piece + without splitting. + + thp_swpout_fallback (npn) + Number of transparent hugepages which were split before swapout. + Usually because failed to allocate some continuous swap space + for the huge page. + memory.numa_stat A read-only nested-keyed file which exists on non-root cgroups.
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2d2cada8a8a4..c61c90ea72a4 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -704,6 +704,8 @@ static const unsigned int memcg_vm_event_stat[] = { #ifdef CONFIG_TRANSPARENT_HUGEPAGE THP_FAULT_ALLOC, THP_COLLAPSE_ALLOC, + THP_SWPOUT, + THP_SWPOUT_FALLBACK, #endif };
diff --git a/mm/page_io.c b/mm/page_io.c index fe4c21af23f2..cb559ae324c6 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -208,8 +208,10 @@ int swap_writepage(struct page *page, struct writeback_control *wbc) static inline void count_swpout_vm_event(struct folio *folio) { #ifdef CONFIG_TRANSPARENT_HUGEPAGE - if (unlikely(folio_test_pmd_mappable(folio))) + if (unlikely(folio_test_pmd_mappable(folio))) { + count_memcg_folio_events(folio, THP_SWPOUT, 1); count_vm_event(THP_SWPOUT); + } #endif count_vm_events(PSWPOUT, folio_nr_pages(folio)); } @@ -278,9 +280,6 @@ static void sio_write_complete(struct kiocb *iocb, long ret) set_page_dirty(page); ClearPageReclaim(page); } - } else { - for (p = 0; p < sio->pages; p++) - count_swpout_vm_event(page_folio(sio->bvec[p].bv_page)); }
for (p = 0; p < sio->pages; p++) @@ -296,6 +295,7 @@ static void swap_writepage_fs(struct page *page, struct writeback_control *wbc) struct file *swap_file = sis->swap_file; loff_t pos = page_file_offset(page);
+ count_swpout_vm_event(page_folio(page)); set_page_writeback(page); unlock_page(page); if (wbc->swap_plug) diff --git a/mm/vmscan.c b/mm/vmscan.c index 258f5472f1e9..774bae2f54d7 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1922,6 +1922,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, folio_list)) goto activate_locked; #ifdef CONFIG_TRANSPARENT_HUGEPAGE + count_memcg_folio_events(folio, THP_SWPOUT_FALLBACK, 1); count_vm_event(THP_SWPOUT_FALLBACK); #endif if (!add_to_swap(folio)) -- 2.50.1
From: Domenico Cerasuolo cerasuolodomenico@gmail.com
[ Upstream commit 7108cc3f765cafd48a6a35f8add140beaecfa75b ]
Since zswap now writes back pages from memcg-specific LRUs, we now need a new stat to show writebacks count for each memcg.
[nphamcs@gmail.com: rename ZSWP_WB to ZSWPWB] Link: https://lkml.kernel.org/r/20231205193307.2432803-1-nphamcs@gmail.com Link: https://lkml.kernel.org/r/20231130194023.4102148-5-nphamcs@gmail.com Suggested-by: Nhat Pham nphamcs@gmail.com Signed-off-by: Domenico Cerasuolo cerasuolodomenico@gmail.com Signed-off-by: Nhat Pham nphamcs@gmail.com Tested-by: Bagas Sanjaya bagasdotme@gmail.com Reviewed-by: Yosry Ahmed yosryahmed@google.com Cc: Chris Li chrisl@kernel.org Cc: Dan Streetman ddstreet@ieee.org Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Muchun Song muchun.song@linux.dev Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Seth Jennings sjenning@redhat.com Cc: Shakeel Butt shakeelb@google.com Cc: Shuah Khan shuah@kernel.org Cc: Vitaly Wool vitaly.wool@konsulko.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Leon Huang Fu leon.huangfu@shopee.com --- include/linux/vm_event_item.h | 1 + mm/memcontrol.c | 1 + mm/vmstat.c | 1 + mm/zswap.c | 4 ++++ 4 files changed, 7 insertions(+)
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h index 8abfa1240040..b61796a35d2b 100644 --- a/include/linux/vm_event_item.h +++ b/include/linux/vm_event_item.h @@ -145,6 +145,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, #ifdef CONFIG_ZSWAP ZSWPIN, ZSWPOUT, + ZSWPWB, #endif #ifdef CONFIG_X86 DIRECT_MAP_LEVEL2_SPLIT, diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c61c90ea72a4..03a984287e5b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -700,6 +700,7 @@ static const unsigned int memcg_vm_event_stat[] = { #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP) ZSWPIN, ZSWPOUT, + ZSWPWB, #endif #ifdef CONFIG_TRANSPARENT_HUGEPAGE THP_FAULT_ALLOC, diff --git a/mm/vmstat.c b/mm/vmstat.c index 57891697846b..3630c6e2bb41 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1397,6 +1397,7 @@ const char * const vmstat_text[] = { #ifdef CONFIG_ZSWAP "zswpin", "zswpout", + "zswpwb", #endif #ifdef CONFIG_X86 "direct_map_level2_splits", diff --git a/mm/zswap.c b/mm/zswap.c index 69681b9173fd..a3459440fc31 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -674,6 +674,10 @@ static int zswap_reclaim_entry(struct zswap_pool *pool) goto put_unlock; }
+ if (entry->objcg) + count_objcg_event(entry->objcg, ZSWPWB); + + count_vm_event(ZSWPWB); /* * Writeback started successfully, the page now belongs to the * swapcache. Drop the entry from zswap - unless invalidate already -- 2.50.1
From: Yosry Ahmed yosryahmed@google.com
[ Upstream commit 508bed884767a8eb394640bae9edcdf082816c43 ]
Patch series "mm: memcg: subtree stats flushing and thresholds", v4.
This series attempts to address shortages in today's approach for memcg stats flushing, namely occasionally stale or expensive stat reads. The series does so by changing the threshold that we use to decide whether to trigger a flush to be per memcg instead of global (patch 3), and then changing flushing to be per memcg (i.e. subtree flushes) instead of global (patch 5).
This patch (of 5):
flush_next_time is an inaccurate name. It's not the next time that periodic flushing will happen, it's rather the next time that ratelimited flushing can happen if the periodic flusher is late.
Simplify its semantics by just storing the timestamp of the last flush instead, flush_last_time. Move the 2*FLUSH_TIME addition to mem_cgroup_flush_stats_ratelimited(), and add a comment explaining it. This way, all the ratelimiting semantics live in one place.
No functional change intended.
Link: https://lkml.kernel.org/r/20231129032154.3710765-1-yosryahmed@google.com Link: https://lkml.kernel.org/r/20231129032154.3710765-2-yosryahmed@google.com Signed-off-by: Yosry Ahmed yosryahmed@google.com Tested-by: Domenico Cerasuolo cerasuolodomenico@gmail.com Acked-by: Shakeel Butt shakeelb@google.com Acked-by: Chris Li chrisl@kernel.org (Google) Tested-by: Bagas Sanjaya bagasdotme@gmail.com Cc: Greg Thelen gthelen@google.com Cc: Ivan Babrou ivan@cloudflare.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Michal Koutny mkoutny@suse.com Cc: Muchun Song muchun.song@linux.dev Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Tejun Heo tj@kernel.org Cc: Waiman Long longman@redhat.com Cc: Wei Xu weixugc@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Leon Huang Fu leon.huangfu@shopee.com --- mm/memcontrol.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 03a984287e5b..433cd273006d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -590,7 +590,7 @@ static DECLARE_DEFERRABLE_WORK(stats_flush_dwork, flush_memcg_stats_dwork); static DEFINE_PER_CPU(unsigned int, stats_updates); static atomic_t stats_flush_ongoing = ATOMIC_INIT(0); static atomic_t stats_flush_threshold = ATOMIC_INIT(0); -static u64 flush_next_time; +static u64 flush_last_time;
#define FLUSH_TIME (2UL*HZ)
@@ -650,7 +650,7 @@ static void do_flush_stats(void) atomic_xchg(&stats_flush_ongoing, 1)) return;
- WRITE_ONCE(flush_next_time, jiffies_64 + 2*FLUSH_TIME); + WRITE_ONCE(flush_last_time, jiffies_64);
cgroup_rstat_flush(root_mem_cgroup->css.cgroup);
@@ -666,7 +666,8 @@ void mem_cgroup_flush_stats(void)
void mem_cgroup_flush_stats_ratelimited(void) { - if (time_after64(jiffies_64, READ_ONCE(flush_next_time))) + /* Only flush if the periodic flusher is one full cycle late */ + if (time_after64(jiffies_64, READ_ONCE(flush_last_time) + 2*FLUSH_TIME)) mem_cgroup_flush_stats(); }
-- 2.50.1
From: Yosry Ahmed yosryahmed@google.com
[ Upstream commit e0bf1dc859fdd08ef738824710770a30a8069433 ]
The following patch will make use of those structs in the flushing code, so move their definitions (and a few other dependencies) a little bit up to reduce the diff noise in the following patch.
No functional change intended.
Link: https://lkml.kernel.org/r/20231129032154.3710765-3-yosryahmed@google.com Signed-off-by: Yosry Ahmed yosryahmed@google.com Tested-by: Domenico Cerasuolo cerasuolodomenico@gmail.com Acked-by: Shakeel Butt shakeelb@google.com Cc: Chris Li chrisl@kernel.org Cc: Greg Thelen gthelen@google.com Cc: Ivan Babrou ivan@cloudflare.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Michal Koutny mkoutny@suse.com Cc: Muchun Song muchun.song@linux.dev Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Tejun Heo tj@kernel.org Cc: Waiman Long longman@redhat.com Cc: Wei Xu weixugc@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Leon Huang Fu leon.huangfu@shopee.com --- mm/memcontrol.c | 148 ++++++++++++++++++++++++------------------------ 1 file changed, 74 insertions(+), 74 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 433cd273006d..157be6820fd1 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -570,6 +570,80 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz) return mz; }
+/* Subset of vm_event_item to report for memcg event stats */ +static const unsigned int memcg_vm_event_stat[] = { + PGPGIN, + PGPGOUT, + PGSCAN_KSWAPD, + PGSCAN_DIRECT, + PGSCAN_KHUGEPAGED, + PGSTEAL_KSWAPD, + PGSTEAL_DIRECT, + PGSTEAL_KHUGEPAGED, + PGFAULT, + PGMAJFAULT, + PGREFILL, + PGACTIVATE, + PGDEACTIVATE, + PGLAZYFREE, + PGLAZYFREED, +#if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP) + ZSWPIN, + ZSWPOUT, + ZSWPWB, +#endif +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + THP_FAULT_ALLOC, + THP_COLLAPSE_ALLOC, + THP_SWPOUT, + THP_SWPOUT_FALLBACK, +#endif +}; + +#define NR_MEMCG_EVENTS ARRAY_SIZE(memcg_vm_event_stat) +static int mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly; + +static void init_memcg_events(void) +{ + int i; + + for (i = 0; i < NR_MEMCG_EVENTS; ++i) + mem_cgroup_events_index[memcg_vm_event_stat[i]] = i + 1; +} + +static inline int memcg_events_index(enum vm_event_item idx) +{ + return mem_cgroup_events_index[idx] - 1; +} + +struct memcg_vmstats_percpu { + /* Local (CPU and cgroup) page state & events */ + long state[MEMCG_NR_STAT]; + unsigned long events[NR_MEMCG_EVENTS]; + + /* Delta calculation for lockless upward propagation */ + long state_prev[MEMCG_NR_STAT]; + unsigned long events_prev[NR_MEMCG_EVENTS]; + + /* Cgroup1: threshold notifications & softlimit tree updates */ + unsigned long nr_page_events; + unsigned long targets[MEM_CGROUP_NTARGETS]; +}; + +struct memcg_vmstats { + /* Aggregated (CPU and subtree) page state & events */ + long state[MEMCG_NR_STAT]; + unsigned long events[NR_MEMCG_EVENTS]; + + /* Non-hierarchical (CPU aggregated) page state & events */ + long state_local[MEMCG_NR_STAT]; + unsigned long events_local[NR_MEMCG_EVENTS]; + + /* Pending child counts during tree propagation */ + long state_pending[MEMCG_NR_STAT]; + unsigned long events_pending[NR_MEMCG_EVENTS]; +}; + /* * memcg and lruvec stats flushing * @@ -681,80 +755,6 @@ static void flush_memcg_stats_dwork(struct work_struct *w) queue_delayed_work(system_unbound_wq, &stats_flush_dwork, FLUSH_TIME); }
-/* Subset of vm_event_item to report for memcg event stats */ -static const unsigned int memcg_vm_event_stat[] = { - PGPGIN, - PGPGOUT, - PGSCAN_KSWAPD, - PGSCAN_DIRECT, - PGSCAN_KHUGEPAGED, - PGSTEAL_KSWAPD, - PGSTEAL_DIRECT, - PGSTEAL_KHUGEPAGED, - PGFAULT, - PGMAJFAULT, - PGREFILL, - PGACTIVATE, - PGDEACTIVATE, - PGLAZYFREE, - PGLAZYFREED, -#if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP) - ZSWPIN, - ZSWPOUT, - ZSWPWB, -#endif -#ifdef CONFIG_TRANSPARENT_HUGEPAGE - THP_FAULT_ALLOC, - THP_COLLAPSE_ALLOC, - THP_SWPOUT, - THP_SWPOUT_FALLBACK, -#endif -}; - -#define NR_MEMCG_EVENTS ARRAY_SIZE(memcg_vm_event_stat) -static int mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly; - -static void init_memcg_events(void) -{ - int i; - - for (i = 0; i < NR_MEMCG_EVENTS; ++i) - mem_cgroup_events_index[memcg_vm_event_stat[i]] = i + 1; -} - -static inline int memcg_events_index(enum vm_event_item idx) -{ - return mem_cgroup_events_index[idx] - 1; -} - -struct memcg_vmstats_percpu { - /* Local (CPU and cgroup) page state & events */ - long state[MEMCG_NR_STAT]; - unsigned long events[NR_MEMCG_EVENTS]; - - /* Delta calculation for lockless upward propagation */ - long state_prev[MEMCG_NR_STAT]; - unsigned long events_prev[NR_MEMCG_EVENTS]; - - /* Cgroup1: threshold notifications & softlimit tree updates */ - unsigned long nr_page_events; - unsigned long targets[MEM_CGROUP_NTARGETS]; -}; - -struct memcg_vmstats { - /* Aggregated (CPU and subtree) page state & events */ - long state[MEMCG_NR_STAT]; - unsigned long events[NR_MEMCG_EVENTS]; - - /* Non-hierarchical (CPU aggregated) page state & events */ - long state_local[MEMCG_NR_STAT]; - unsigned long events_local[NR_MEMCG_EVENTS]; - - /* Pending child counts during tree propagation */ - long state_pending[MEMCG_NR_STAT]; - unsigned long events_pending[NR_MEMCG_EVENTS]; -}; - unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx) { long x = READ_ONCE(memcg->vmstats->state[idx]); -- 2.50.1
From: Yosry Ahmed yosryahmed@google.com
[ Upstream commit 8d59d2214c2362e7a9d185d80b613e632581af7b ]
A global counter for the magnitude of memcg stats update is maintained on the memcg side to avoid invoking rstat flushes when the pending updates are not significant. This avoids unnecessary flushes, which are not very cheap even if there isn't a lot of stats to flush. It also avoids unnecessary lock contention on the underlying global rstat lock.
Make this threshold per-memcg. The scheme is followed where percpu (now also per-memcg) counters are incremented in the update path, and only propagated to per-memcg atomics when they exceed a certain threshold.
This provides two benefits: (a) On large machines with a lot of memcgs, the global threshold can be reached relatively fast, so guarding the underlying lock becomes less effective. Making the threshold per-memcg avoids this.
(b) Having a global threshold makes it hard to do subtree flushes, as we cannot reset the global counter except for a full flush. Per-memcg counters removes this as a blocker from doing subtree flushes, which helps avoid unnecessary work when the stats of a small subtree are needed.
Nothing is free, of course. This comes at a cost: (a) A new per-cpu counter per memcg, consuming NR_CPUS * NR_MEMCGS * 4 bytes. The extra memory usage is insigificant.
(b) More work on the update side, although in the common case it will only be percpu counter updates. The amount of work scales with the number of ancestors (i.e. tree depth). This is not a new concept, adding a cgroup to the rstat tree involves a parent loop, so is charging. Testing results below show no significant regressions.
(c) The error margin in the stats for the system as a whole increases from NR_CPUS * MEMCG_CHARGE_BATCH to NR_CPUS * MEMCG_CHARGE_BATCH * NR_MEMCGS. This is probably fine because we have a similar per-memcg error in charges coming from percpu stocks, and we have a periodic flusher that makes sure we always flush all the stats every 2s anyway.
This patch was tested to make sure no significant regressions are introduced on the update path as follows. The following benchmarks were ran in a cgroup that is 2 levels deep (/sys/fs/cgroup/a/b/):
(1) Running 22 instances of netperf on a 44 cpu machine with hyperthreading disabled. All instances are run in a level 2 cgroup, as well as netserver: # netserver -6 # netperf -6 -H ::1 -l 60 -t TCP_SENDFILE -- -m 10K
Averaging 20 runs, the numbers are as follows: Base: 40198.0 mbps Patched: 38629.7 mbps (-3.9%)
The regression is minimal, especially for 22 instances in the same cgroup sharing all ancestors (so updating the same atomics).
(2) will-it-scale page_fault tests. These tests (specifically per_process_ops in page_fault3 test) detected a 25.9% regression before for a change in the stats update path [1]. These are the numbers from 10 runs (+ is good) on a machine with 256 cpus:
LABEL | MEAN | MEDIAN | STDDEV | ------------------------------+-------------+-------------+------------- page_fault1_per_process_ops | | | | (A) base | 270249.164 | 265437.000 | 13451.836 | (B) patched | 261368.709 | 255725.000 | 13394.767 | | -3.29% | -3.66% | | page_fault1_per_thread_ops | | | | (A) base | 242111.345 | 239737.000 | 10026.031 | (B) patched | 237057.109 | 235305.000 | 9769.687 | | -2.09% | -1.85% | | page_fault1_scalability | | | (A) base | 0.034387 | 0.035168 | 0.0018283 | (B) patched | 0.033988 | 0.034573 | 0.0018056 | | -1.16% | -1.69% | | page_fault2_per_process_ops | | | (A) base | 203561.836 | 203301.000 | 2550.764 | (B) patched | 197195.945 | 197746.000 | 2264.263 | | -3.13% | -2.73% | | page_fault2_per_thread_ops | | | (A) base | 171046.473 | 170776.000 | 1509.679 | (B) patched | 166626.327 | 166406.000 | 768.753 | | -2.58% | -2.56% | | page_fault2_scalability | | | (A) base | 0.054026 | 0.053821 | 0.00062121 | (B) patched | 0.053329 | 0.05306 | 0.00048394 | | -1.29% | -1.41% | | page_fault3_per_process_ops | | | (A) base | 1295807.782 | 1297550.000 | 5907.585 | (B) patched | 1275579.873 | 1273359.000 | 8759.160 | | -1.56% | -1.86% | | page_fault3_per_thread_ops | | | (A) base | 391234.164 | 390860.000 | 1760.720 | (B) patched | 377231.273 | 376369.000 | 1874.971 | | -3.58% | -3.71% | | page_fault3_scalability | | | (A) base | 0.60369 | 0.60072 | 0.0083029 | (B) patched | 0.61733 | 0.61544 | 0.009855 | | +2.26% | +2.45% | |
All regressions seem to be minimal, and within the normal variance for the benchmark. The fix for [1] assumes that 3% is noise -- and there were no further practical complaints), so hopefully this means that such variations in these microbenchmarks do not reflect on practical workloads.
(3) I also ran stress-ng in a nested cgroup and did not observe any obvious regressions.
[1]https://lore.kernel.org/all/20190520063534.GB19312@shao2-debian/
Link: https://lkml.kernel.org/r/20231129032154.3710765-4-yosryahmed@google.com Signed-off-by: Yosry Ahmed yosryahmed@google.com Suggested-by: Johannes Weiner hannes@cmpxchg.org Tested-by: Domenico Cerasuolo cerasuolodomenico@gmail.com Acked-by: Shakeel Butt shakeelb@google.com Cc: Chris Li chrisl@kernel.org Cc: Greg Thelen gthelen@google.com Cc: Ivan Babrou ivan@cloudflare.com Cc: Michal Hocko mhocko@kernel.org Cc: Michal Koutny mkoutny@suse.com Cc: Muchun Song muchun.song@linux.dev Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Tejun Heo tj@kernel.org Cc: Waiman Long longman@redhat.com Cc: Wei Xu weixugc@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Leon Huang Fu leon.huangfu@shopee.com --- mm/memcontrol.c | 50 +++++++++++++++++++++++++++++++++---------------- 1 file changed, 34 insertions(+), 16 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 157be6820fd1..c31a5364f325 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -628,6 +628,9 @@ struct memcg_vmstats_percpu { /* Cgroup1: threshold notifications & softlimit tree updates */ unsigned long nr_page_events; unsigned long targets[MEM_CGROUP_NTARGETS]; + + /* Stats updates since the last flush */ + unsigned int stats_updates; };
struct memcg_vmstats { @@ -642,6 +645,9 @@ struct memcg_vmstats { /* Pending child counts during tree propagation */ long state_pending[MEMCG_NR_STAT]; unsigned long events_pending[NR_MEMCG_EVENTS]; + + /* Stats updates since the last flush */ + atomic64_t stats_updates; };
/* @@ -661,9 +667,7 @@ struct memcg_vmstats { */ static void flush_memcg_stats_dwork(struct work_struct *w); static DECLARE_DEFERRABLE_WORK(stats_flush_dwork, flush_memcg_stats_dwork); -static DEFINE_PER_CPU(unsigned int, stats_updates); static atomic_t stats_flush_ongoing = ATOMIC_INIT(0); -static atomic_t stats_flush_threshold = ATOMIC_INIT(0); static u64 flush_last_time;
#define FLUSH_TIME (2UL*HZ) @@ -690,26 +694,37 @@ static void memcg_stats_unlock(void) preempt_enable_nested(); }
+ +static bool memcg_should_flush_stats(struct mem_cgroup *memcg) +{ + return atomic64_read(&memcg->vmstats->stats_updates) > + MEMCG_CHARGE_BATCH * num_online_cpus(); +} + static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val) { + int cpu = smp_processor_id(); unsigned int x;
if (!val) return;
- cgroup_rstat_updated(memcg->css.cgroup, smp_processor_id()); + cgroup_rstat_updated(memcg->css.cgroup, cpu); + + for (; memcg; memcg = parent_mem_cgroup(memcg)) { + x = __this_cpu_add_return(memcg->vmstats_percpu->stats_updates, + abs(val)); + + if (x < MEMCG_CHARGE_BATCH) + continue;
- x = __this_cpu_add_return(stats_updates, abs(val)); - if (x > MEMCG_CHARGE_BATCH) { /* - * If stats_flush_threshold exceeds the threshold - * (>num_online_cpus()), cgroup stats update will be triggered - * in __mem_cgroup_flush_stats(). Increasing this var further - * is redundant and simply adds overhead in atomic update. + * If @memcg is already flush-able, increasing stats_updates is + * redundant. Avoid the overhead of the atomic update. */ - if (atomic_read(&stats_flush_threshold) <= num_online_cpus()) - atomic_add(x / MEMCG_CHARGE_BATCH, &stats_flush_threshold); - __this_cpu_write(stats_updates, 0); + if (!memcg_should_flush_stats(memcg)) + atomic64_add(x, &memcg->vmstats->stats_updates); + __this_cpu_write(memcg->vmstats_percpu->stats_updates, 0); } }
@@ -728,13 +743,12 @@ static void do_flush_stats(void)
cgroup_rstat_flush(root_mem_cgroup->css.cgroup);
- atomic_set(&stats_flush_threshold, 0); atomic_set(&stats_flush_ongoing, 0); }
void mem_cgroup_flush_stats(void) { - if (atomic_read(&stats_flush_threshold) > num_online_cpus()) + if (memcg_should_flush_stats(root_mem_cgroup)) do_flush_stats(); }
@@ -748,8 +762,8 @@ void mem_cgroup_flush_stats_ratelimited(void) static void flush_memcg_stats_dwork(struct work_struct *w) { /* - * Always flush here so that flushing in latency-sensitive paths is - * as cheap as possible. + * Deliberately ignore memcg_should_flush_stats() here so that flushing + * in latency-sensitive paths is as cheap as possible. */ do_flush_stats(); queue_delayed_work(system_unbound_wq, &stats_flush_dwork, FLUSH_TIME); @@ -5658,6 +5672,10 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu) } } } + statc->stats_updates = 0; + /* We are in a per-cpu loop here, only do the atomic write once */ + if (atomic64_read(&memcg->vmstats->stats_updates)) + atomic64_set(&memcg->vmstats->stats_updates, 0); }
#ifdef CONFIG_MMU -- 2.50.1
From: Yosry Ahmed yosryahmed@google.com
[ Upstream commit b006847222623ac3cda8589d15379eac86a2bcb7 ]
The workingset code flushes the stats in workingset_refault() to get accurate stats of the eviction memcg. In preparation for more scoped flushed and passing the eviction memcg to the flush call, move the call to workingset_test_recent() where we have a pointer to the eviction memcg.
The flush call is sleepable, and cannot be made in an rcu read section. Hence, minimize the rcu read section by also moving it into workingset_test_recent(). Furthermore, instead of holding the rcu read lock throughout workingset_test_recent(), only hold it briefly to get a ref on the eviction memcg. This allows us to make the flush call after we get the eviction memcg.
As for workingset_refault(), nothing else there appears to be protected by rcu. The memcg of the faulted folio (which is not necessarily the same as the eviction memcg) is protected by the folio lock, which is held from all callsites. Add a VM_BUG_ON() to make sure this doesn't change from under us.
No functional change intended.
Link: https://lkml.kernel.org/r/20231129032154.3710765-5-yosryahmed@google.com Signed-off-by: Yosry Ahmed yosryahmed@google.com Tested-by: Domenico Cerasuolo cerasuolodomenico@gmail.com Acked-by: Shakeel Butt shakeelb@google.com Cc: Chris Li chrisl@kernel.org Cc: Greg Thelen gthelen@google.com Cc: Ivan Babrou ivan@cloudflare.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Michal Koutny mkoutny@suse.com Cc: Muchun Song muchun.song@linux.dev Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Tejun Heo tj@kernel.org Cc: Waiman Long longman@redhat.com Cc: Wei Xu weixugc@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Leon Huang Fu leon.huangfu@shopee.com --- mm/workingset.c | 36 ++++++++++++++++++++++++------------ 1 file changed, 24 insertions(+), 12 deletions(-)
diff --git a/mm/workingset.c b/mm/workingset.c index 9110957bec5b..6e61ad08df75 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -425,8 +425,16 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset) struct pglist_data *pgdat; unsigned long eviction;
- if (lru_gen_enabled()) - return lru_gen_test_recent(shadow, file, &eviction_lruvec, &eviction, workingset); + rcu_read_lock(); + + if (lru_gen_enabled()) { + bool recent = lru_gen_test_recent(shadow, file, + &eviction_lruvec, &eviction, workingset); + + rcu_read_unlock(); + return recent; + } +
unpack_shadow(shadow, &memcgid, &pgdat, &eviction, workingset); eviction <<= bucket_order; @@ -448,8 +456,16 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset) * configurations instead. */ eviction_memcg = mem_cgroup_from_id(memcgid); - if (!mem_cgroup_disabled() && !eviction_memcg) + if (!mem_cgroup_disabled() && + (!eviction_memcg || !mem_cgroup_tryget(eviction_memcg))) { + rcu_read_unlock(); return false; + } + + rcu_read_unlock(); + + /* Flush stats (and potentially sleep) outside the RCU read section */ + mem_cgroup_flush_stats_ratelimited();
eviction_lruvec = mem_cgroup_lruvec(eviction_memcg, pgdat); refault = atomic_long_read(&eviction_lruvec->nonresident_age); @@ -493,6 +509,7 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset) } }
+ mem_cgroup_put(eviction_memcg); return refault_distance <= workingset_size; }
@@ -519,19 +536,16 @@ void workingset_refault(struct folio *folio, void *shadow) return; }
- /* Flush stats (and potentially sleep) before holding RCU read lock */ - mem_cgroup_flush_stats_ratelimited(); - - rcu_read_lock(); - /* * The activation decision for this folio is made at the level * where the eviction occurred, as that is where the LRU order * during folio reclaim is being determined. * * However, the cgroup that will own the folio is the one that - * is actually experiencing the refault event. + * is actually experiencing the refault event. Make sure the folio is + * locked to guarantee folio_memcg() stability throughout. */ + VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); nr = folio_nr_pages(folio); memcg = folio_memcg(folio); pgdat = folio_pgdat(folio); @@ -540,7 +554,7 @@ void workingset_refault(struct folio *folio, void *shadow) mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file, nr);
if (!workingset_test_recent(shadow, file, &workingset)) - goto out; + return;
folio_set_active(folio); workingset_age_nonresident(lruvec, nr); @@ -556,8 +570,6 @@ void workingset_refault(struct folio *folio, void *shadow) lru_note_cost_refault(folio); mod_lruvec_state(lruvec, WORKINGSET_RESTORE_BASE + file, nr); } -out: - rcu_read_unlock(); }
/** -- 2.50.1
From: Yosry Ahmed yosryahmed@google.com
[ Upstream commit 7d7ef0a4686abe43cd76a141b340a348f45ecdf2 ]
Stats flushing for memcg currently follows the following rules: - Always flush the entire memcg hierarchy (i.e. flush the root). - Only one flusher is allowed at a time. If someone else tries to flush concurrently, they skip and return immediately. - A periodic flusher flushes all the stats every 2 seconds.
The reason this approach is followed is because all flushes are serialized by a global rstat spinlock. On the memcg side, flushing is invoked from userspace reads as well as in-kernel flushers (e.g. reclaim, refault, etc). This approach aims to avoid serializing all flushers on the global lock, which can cause a significant performance hit under high concurrency.
This approach has the following problems: - Occasionally a userspace read of the stats of a non-root cgroup will be too expensive as it has to flush the entire hierarchy [1]. - Sometimes the stats accuracy are compromised if there is an ongoing flush, and we skip and return before the subtree of interest is actually flushed, yielding stale stats (by up to 2s due to periodic flushing). This is more visible when reading stats from userspace, but can also affect in-kernel flushers.
The latter problem is particulary a concern when userspace reads stats after an event occurs, but gets stats from before the event. Examples: - When memory usage / pressure spikes, a userspace OOM handler may look at the stats of different memcgs to select a victim based on various heuristics (e.g. how much private memory will be freed by killing this). Reading stale stats from before the usage spike in this case may cause a wrongful OOM kill. - A proactive reclaimer may read the stats after writing to memory.reclaim to measure the success of the reclaim operation. Stale stats from before reclaim may give a false negative. - Reading the stats of a parent and a child memcg may be inconsistent (child larger than parent), if the flush doesn't happen when the parent is read, but happens when the child is read.
As for in-kernel flushers, they will occasionally get stale stats. No regressions are currently known from this, but if there are regressions, they would be very difficult to debug and link to the source of the problem.
This patch aims to fix these problems by restoring subtree flushing, and removing the unified/coalesced flushing logic that skips flushing if there is an ongoing flush. This change would introduce a significant regression with global stats flushing thresholds. With per-memcg stats flushing thresholds, this seems to perform really well. The thresholds protect the underlying lock from unnecessary contention.
This patch was tested in two ways to ensure the latency of flushing is up to par, on a machine with 384 cpus:
- A synthetic test with 5000 concurrent workers in 500 cgroups doing allocations and reclaim, as well as 1000 readers for memory.stat (variation of [2]). No regressions were noticed in the total runtime. Note that significant regressions in this test are observed with global stats thresholds, but not with per-memcg thresholds.
- A synthetic stress test for concurrently reading memcg stats while memory allocation/freeing workers are running in the background, provided by Wei Xu [3]. With 250k threads reading the stats every 100ms in 50k cgroups, 99.9% of reads take <= 50us. Less than 0.01% of reads take more than 1ms, and no reads take more than 100ms.
[1] https://lore.kernel.org/lkml/CABWYdi0c6__rh-K7dcM_pkf9BJdTRtAU08M43KO9ME4-ds... [2] https://lore.kernel.org/lkml/CAJD7tka13M-zVZTyQJYL1iUAYvuQ1fcHbCjcOBZcz6POYT... [3] https://lore.kernel.org/lkml/CAAPL-u9D2b=iF5Lf_cRnKxUfkiEe0AMDTu6yhrUAzX0b6a...
[akpm@linux-foundation.org: fix mm/zswap.c] [yosryahmed@google.com: remove stats flushing mutex] Link: https://lkml.kernel.org/r/CAJD7tkZgP3m-VVPn+fF_YuvXeQYK=tZZjJHj=dzD=CcSSpp2q... Link: https://lkml.kernel.org/r/20231129032154.3710765-6-yosryahmed@google.com Signed-off-by: Yosry Ahmed yosryahmed@google.com Tested-by: Domenico Cerasuolo cerasuolodomenico@gmail.com Acked-by: Shakeel Butt shakeelb@google.com Cc: Chris Li chrisl@kernel.org Cc: Greg Thelen gthelen@google.com Cc: Ivan Babrou ivan@cloudflare.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Michal Koutny mkoutny@suse.com Cc: Muchun Song muchun.song@linux.dev Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Tejun Heo tj@kernel.org Cc: Waiman Long longman@redhat.com Cc: Wei Xu weixugc@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Leon Huang Fu leon.huangfu@shopee.com --- include/linux/memcontrol.h | 8 ++--- mm/memcontrol.c | 68 ++++++++++++++++++++++---------------- mm/vmscan.c | 2 +- mm/workingset.c | 10 ++++-- 4 files changed, 51 insertions(+), 37 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index b1fdb1554f2f..8aee8b75aad0 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1039,8 +1039,8 @@ static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, return x; }
-void mem_cgroup_flush_stats(void); -void mem_cgroup_flush_stats_ratelimited(void); +void mem_cgroup_flush_stats(struct mem_cgroup *memcg); +void mem_cgroup_flush_stats_ratelimited(struct mem_cgroup *memcg);
void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx, int val); @@ -1515,11 +1515,11 @@ static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, return node_page_state(lruvec_pgdat(lruvec), idx); }
-static inline void mem_cgroup_flush_stats(void) +static inline void mem_cgroup_flush_stats(struct mem_cgroup *memcg) { }
-static inline void mem_cgroup_flush_stats_ratelimited(void) +static inline void mem_cgroup_flush_stats_ratelimited(struct mem_cgroup *memcg) { }
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c31a5364f325..d3f4486a45d8 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -667,7 +667,6 @@ struct memcg_vmstats { */ static void flush_memcg_stats_dwork(struct work_struct *w); static DECLARE_DEFERRABLE_WORK(stats_flush_dwork, flush_memcg_stats_dwork); -static atomic_t stats_flush_ongoing = ATOMIC_INIT(0); static u64 flush_last_time;
#define FLUSH_TIME (2UL*HZ) @@ -728,35 +727,40 @@ static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val) } }
-static void do_flush_stats(void) +static void do_flush_stats(struct mem_cgroup *memcg) { - /* - * We always flush the entire tree, so concurrent flushers can just - * skip. This avoids a thundering herd problem on the rstat global lock - * from memcg flushers (e.g. reclaim, refault, etc). - */ - if (atomic_read(&stats_flush_ongoing) || - atomic_xchg(&stats_flush_ongoing, 1)) - return; - - WRITE_ONCE(flush_last_time, jiffies_64); - - cgroup_rstat_flush(root_mem_cgroup->css.cgroup); + if (mem_cgroup_is_root(memcg)) + WRITE_ONCE(flush_last_time, jiffies_64);
- atomic_set(&stats_flush_ongoing, 0); + cgroup_rstat_flush(memcg->css.cgroup); }
-void mem_cgroup_flush_stats(void) +/* + * mem_cgroup_flush_stats - flush the stats of a memory cgroup subtree + * @memcg: root of the subtree to flush + * + * Flushing is serialized by the underlying global rstat lock. There is also a + * minimum amount of work to be done even if there are no stat updates to flush. + * Hence, we only flush the stats if the updates delta exceeds a threshold. This + * avoids unnecessary work and contention on the underlying lock. + */ +void mem_cgroup_flush_stats(struct mem_cgroup *memcg) { - if (memcg_should_flush_stats(root_mem_cgroup)) - do_flush_stats(); + if (mem_cgroup_disabled()) + return; + + if (!memcg) + memcg = root_mem_cgroup; + + if (memcg_should_flush_stats(memcg)) + do_flush_stats(memcg); }
-void mem_cgroup_flush_stats_ratelimited(void) +void mem_cgroup_flush_stats_ratelimited(struct mem_cgroup *memcg) { /* Only flush if the periodic flusher is one full cycle late */ if (time_after64(jiffies_64, READ_ONCE(flush_last_time) + 2*FLUSH_TIME)) - mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(memcg); }
static void flush_memcg_stats_dwork(struct work_struct *w) @@ -765,7 +769,7 @@ static void flush_memcg_stats_dwork(struct work_struct *w) * Deliberately ignore memcg_should_flush_stats() here so that flushing * in latency-sensitive paths is as cheap as possible. */ - do_flush_stats(); + do_flush_stats(root_mem_cgroup); queue_delayed_work(system_unbound_wq, &stats_flush_dwork, FLUSH_TIME); }
@@ -1597,7 +1601,7 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) * * Current memory state: */ - mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(memcg);
for (i = 0; i < ARRAY_SIZE(memory_stats); i++) { u64 size; @@ -4047,7 +4051,7 @@ static int memcg_numa_stat_show(struct seq_file *m, void *v) int nid; struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
- mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(memcg);
for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) { seq_printf(m, "%s=%lu", stat->name, @@ -4122,7 +4126,7 @@ static void memcg1_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
BUILD_BUG_ON(ARRAY_SIZE(memcg1_stat_names) != ARRAY_SIZE(memcg1_stats));
- mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(memcg);
for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) { unsigned long nr; @@ -4624,7 +4628,7 @@ void mem_cgroup_wb_stats(struct bdi_writeback *wb, unsigned long *pfilepages, struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css); struct mem_cgroup *parent;
- mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(memcg);
*pdirty = memcg_page_state(memcg, NR_FILE_DIRTY); *pwriteback = memcg_page_state(memcg, NR_WRITEBACK); @@ -6704,7 +6708,7 @@ static int memory_numa_stat_show(struct seq_file *m, void *v) int i; struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
- mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(memcg);
for (i = 0; i < ARRAY_SIZE(memory_stats); i++) { int nid; @@ -7868,7 +7872,11 @@ bool obj_cgroup_may_zswap(struct obj_cgroup *objcg) break; }
- cgroup_rstat_flush(memcg->css.cgroup); + /* + * mem_cgroup_flush_stats() ignores small changes. Use + * do_flush_stats() directly to get accurate stats for charging. + */ + do_flush_stats(memcg); pages = memcg_page_state(memcg, MEMCG_ZSWAP_B) / PAGE_SIZE; if (pages < max) continue; @@ -7933,8 +7941,10 @@ void obj_cgroup_uncharge_zswap(struct obj_cgroup *objcg, size_t size) static u64 zswap_current_read(struct cgroup_subsys_state *css, struct cftype *cft) { - cgroup_rstat_flush(css->cgroup); - return memcg_page_state(mem_cgroup_from_css(css), MEMCG_ZSWAP_B); + struct mem_cgroup *memcg = mem_cgroup_from_css(css); + + mem_cgroup_flush_stats(memcg); + return memcg_page_state(memcg, MEMCG_ZSWAP_B); }
static int zswap_max_show(struct seq_file *m, void *v) diff --git a/mm/vmscan.c b/mm/vmscan.c index 774bae2f54d7..aba757e5c597 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2911,7 +2911,7 @@ static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc) * Flush the memory cgroup stats, so that we read accurate per-memcg * lruvec stats for heuristics. */ - mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(sc->target_mem_cgroup);
/* * Determine the scan balance between anon and file LRUs. diff --git a/mm/workingset.c b/mm/workingset.c index 6e61ad08df75..7bac9be1b87f 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -464,8 +464,12 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset)
rcu_read_unlock();
- /* Flush stats (and potentially sleep) outside the RCU read section */ - mem_cgroup_flush_stats_ratelimited(); + /* + * Flush stats (and potentially sleep) outside the RCU read section. + * XXX: With per-memcg flushing and thresholding, is ratelimiting + * still needed here? + */ + mem_cgroup_flush_stats_ratelimited(eviction_memcg);
eviction_lruvec = mem_cgroup_lruvec(eviction_memcg, pgdat); refault = atomic_long_read(&eviction_lruvec->nonresident_age); @@ -676,7 +680,7 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker, struct lruvec *lruvec; int i;
- mem_cgroup_flush_stats_ratelimited(); + mem_cgroup_flush_stats_ratelimited(sc->memcg); lruvec = mem_cgroup_lruvec(sc->memcg, NODE_DATA(sc->nid)); for (pages = 0, i = 0; i < NR_LRU_LISTS; i++) pages += lruvec_page_state_local(lruvec, -- 2.50.1
linux-stable-mirror@lists.linaro.org
-
Leon Huang Fu