The patch titled
memcg: use css_tryget in memcg
has been added to the -mm tree. Its filename is
memcg-use-css_tryget-in-memcg.patch
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------------------------------------------------------
Subject: memcg: use css_tryget in memcg
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
css_tryget() newly is added and we can know css is alive or not and get
refcnt of css in very safe way. ("alive" here means "rmdir/destroy" is
not called.)
This patch replaces css_get() to css_tryget(), where I cannot explain
why css_get() is safe. And removes memcg->obsolete flag.
Reviewed-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 96 +++++++++++++++++++++++++++++-----------------
1 file changed, 61 insertions(+), 35 deletions(-)
diff -puN mm/memcontrol.c~memcg-use-css_tryget-in-memcg mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-use-css_tryget-in-memcg
+++ a/mm/memcontrol.c
@@ -162,7 +162,6 @@ struct mem_cgroup {
*/
bool use_hierarchy;
unsigned long last_oom_jiffies;
- int obsolete;
atomic_t refcnt;
unsigned int swappiness;
@@ -283,6 +282,31 @@ struct mem_cgroup *mem_cgroup_from_task(
struct mem_cgroup, css);
}
+static struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
+{
+ struct mem_cgroup *mem = NULL;
+ /*
+ * Because we have no locks, mm->owner's may be being moved to other
+ * cgroup. We use css_tryget() here even if this looks
+ * pessimistic (rather than adding locks here).
+ */
+ rcu_read_lock();
+ do {
+ mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
+ if (unlikely(!mem))
+ break;
+ } while (!css_tryget(&mem->css));
+ rcu_read_unlock();
+ return mem;
+}
+
+static bool mem_cgroup_is_obsolete(struct mem_cgroup *mem)
+{
+ if (!mem)
+ return true;
+ return css_is_removed(&mem->css);
+}
+
/*
* Following LRU functions are allowed to be used without PCG_LOCK.
* Operations are called by routine of global LRU independently from memcg.
@@ -617,8 +641,9 @@ mem_cgroup_get_first_node(struct mem_cgr
{
struct cgroup *cgroup;
struct mem_cgroup *ret;
- bool obsolete = (root_mem->last_scanned_child &&
- root_mem->last_scanned_child->obsolete);
+ bool obsolete;
+
+ obsolete = mem_cgroup_is_obsolete(root_mem->last_scanned_child);
/*
* Scan all children under the mem_cgroup mem
@@ -706,7 +731,7 @@ static int mem_cgroup_hierarchical_recla
next_mem = mem_cgroup_get_first_node(root_mem);
while (next_mem != root_mem) {
- if (next_mem->obsolete) {
+ if (mem_cgroup_is_obsolete(next_mem)) {
mem_cgroup_put(next_mem);
cgroup_lock();
next_mem = mem_cgroup_get_first_node(root_mem);
@@ -764,23 +789,17 @@ static int __mem_cgroup_try_charge(struc
* thread group leader migrates. It's possible that mm is not
* set, if so charge the init_mm (happens for pagecache usage).
*/
- if (likely(!*memcg)) {
- rcu_read_lock();
- mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
- if (unlikely(!mem)) {
- rcu_read_unlock();
- return 0;
- }
- /*
- * For every charge from the cgroup, increment reference count
- */
- css_get(&mem->css);
+ mem = *memcg;
+ if (likely(!mem)) {
+ mem = try_get_mem_cgroup_from_mm(mm);
*memcg = mem;
- rcu_read_unlock();
} else {
- mem = *memcg;
css_get(&mem->css);
}
+ if (unlikely(!mem))
+ return 0;
+
+ VM_BUG_ON(mem_cgroup_is_obsolete(mem));
while (1) {
int ret;
@@ -1067,12 +1086,19 @@ int mem_cgroup_cache_charge(struct page
MEM_CGROUP_CHARGE_TYPE_SHMEM, NULL);
}
+/*
+ * While swap-in, try_charge -> commit or cancel, the page is locked.
+ * And when try_charge() successfully returns, one refcnt to memcg without
+ * struct page_cgroup is aquired. This refcnt will be cumsumed by
+ * "commit()" or removed by "cancel()"
+ */
int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
struct page *page,
gfp_t mask, struct mem_cgroup **ptr)
{
struct mem_cgroup *mem;
swp_entry_t ent;
+ int ret;
if (mem_cgroup_disabled())
return 0;
@@ -1091,10 +1117,15 @@ int mem_cgroup_try_charge_swapin(struct
ent.val = page_private(page);
mem = lookup_swap_cgroup(ent);
- if (!mem || mem->obsolete)
+ if (!mem)
+ goto charge_cur_mm;
+ if (!css_tryget(&mem->css))
goto charge_cur_mm;
*ptr = mem;
- return __mem_cgroup_try_charge(NULL, mask, ptr, true);
+ ret = __mem_cgroup_try_charge(NULL, mask, ptr, true);
+ /* drop extra refcnt from tryget */
+ css_put(&mem->css);
+ return ret;
charge_cur_mm:
if (unlikely(!mm))
mm = &init_mm;
@@ -1125,13 +1156,18 @@ int mem_cgroup_cache_charge_swapin(struc
ent.val = page_private(page);
if (do_swap_account) {
mem = lookup_swap_cgroup(ent);
- if (mem && mem->obsolete)
- mem = NULL;
- if (mem)
- mm = NULL;
+ if (mem) {
+ if (css_tryget(&mem->css))
+ mm = NULL; /* charge to recorded */
+ else
+ mem = NULL; /* charge to current */
+ }
}
ret = mem_cgroup_charge_common(page, mm, mask,
MEM_CGROUP_CHARGE_TYPE_SHMEM, mem);
+ /* drop extra refcnt from tryget */
+ if (mem)
+ css_put(&mem->css);
if (!ret && do_swap_account) {
/* avoid double counting */
@@ -1173,7 +1209,6 @@ void mem_cgroup_commit_charge_swapin(str
struct mem_cgroup *memcg;
memcg = swap_cgroup_record(ent, NULL);
if (memcg) {
- /* If memcg is obsolete, memcg can be != ptr */
res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
mem_cgroup_put(memcg);
}
@@ -1416,14 +1451,9 @@ int mem_cgroup_shrink_usage(struct mm_st
if (!mm)
return 0;
- rcu_read_lock();
- mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
- if (unlikely(!mem)) {
- rcu_read_unlock();
+ mem = try_get_mem_cgroup_from_mm(mm);
+ if (unlikely(!mem))
return 0;
- }
- css_get(&mem->css);
- rcu_read_unlock();
do {
progress = mem_cgroup_hierarchical_reclaim(mem, gfp_mask, true);
@@ -2081,9 +2111,6 @@ static struct mem_cgroup *mem_cgroup_all
* the number of reference from swap_cgroup and free mem_cgroup when
* it goes down to 0.
*
- * When mem_cgroup is destroyed, mem->obsolete will be set to 0 and
- * entry which points to this memcg will be ignore at swapin.
- *
* Removal of cgroup itself succeeds regardless of refs from swap.
*/
@@ -2169,7 +2196,6 @@ static void mem_cgroup_pre_destroy(struc
struct cgroup *cont)
{
struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
- mem->obsolete = 1;
mem_cgroup_force_empty(mem, false);
}
_
Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are
origin.patch
driver-core-unbork-device_release.patch
clocksource-pass-clocksource-to-read-callback-fix.patch
mm-gup-persist-for-write-permission.patch
mm-wp-lock-page-before-deciding-cow.patch
mm-reuse_swap_page-replaces-can_share_swap_page.patch
mm-try_to_free_swap-replaces-remove_exclusive_swap_page.patch
mm-try_to_unuse-check-removing-right-swap.patch
mm-remove-try_to_munlock-from-vmscan.patch
mm-remove-gfp_mask-from-add_to_swap.patch
mm-add-add_to_swap-stub.patch
mm-optimize-get_scan_ratio-for-no-swap.patch
memcg-reclaim-shouldnt-change-zone-recent_rotated-statistics.patch
swapfile-swapon-needs-larger-size-type.patch
swapfile-remove-swp_active-mask.patch
swapfile-remove-surplus-whitespace.patch
swapfile-remove-v0-swap-space-message.patch
swapfile-rearrange-scan-and-swap_info.patch
swapfile-swapon-use-discard-trim.patch
swapfile-swap-allocation-use-discard.patch
swapfile-swapon-randomize-if-nonrot.patch
swapfile-swap-allocation-cycle-if-nonrot.patch
swapfile-change-discard-pgoff_t-to-sector_t.patch
swapfile-change-discard-pgoff_t-to-sector_t-fix.patch
swapfile-let-others-seed-random.patch
mm-remove-config_out_of_line_pfn_to_page.patch
cgroups-make-cgroup-config-a-submenu.patch
cgroups-documentation-updates.patch
cgroups-remove-some-redundant-null-checks.patch
ns_cgroup-remove-unused-spinlock.patch
memcg-fix-a-typo-in-kconfig.patch
cgroups-add-lock-for-child-cgroups-in-cgroup_post_fork.patch
cgroups-fix-cgroup_iter_next-bug.patch
cgroups-dont-put-struct-cgroupfs_root-protected-by-rcu.patch
cgroups-use-task_lock-for-access-tsk-cgroups-safe-in-cgroup_clone.patch
cgroups-call-find_css_set-safely-in-cgroup_attach_task.patch
cgroups-remove-rcu_read_lock-in-cgroupstats_build.patch
cgroups-make-root_list-contains-active-hierarchies-only.patch
cgroups-add-inactive-subsystems-to-rootnodesubsys_list.patch
cgroups-add-inactive-subsystems-to-rootnodesubsys_list-fix.patch
cgroups-introduce-link_css_set-to-remove-duplicate-code.patch
cgroups-introduce-link_css_set-to-remove-duplicate-code-fix.patch
devcgroup-use-list_for_each_entry_rcu.patch
memcg-introduce-charge-commit-cancel-style-of-functions.patch
memcg-introduce-charge-commit-cancel-style-of-functions-fix.patch
memcg-fix-gfp_mask-of-callers-of-charge.patch
memcg-simple-migration-handling.patch
memcg-do-not-recalculate-section-unnecessarily-in-init_section_page_cgroup.patch
memcg-move-all-acccounts-to-parent-at-rmdir.patch
memcg-reduce-size-of-mem_cgroup-by-using-nr_cpu_ids.patch
memcg-new-force_empty-to-free-pages-under-group.patch
memcg-new-force_empty-to-free-pages-under-group-fix.patch
memcg-new-force_empty-to-free-pages-under-group-fix-fix.patch
memcg-handle-swap-caches.patch
memcg-handle-swap-caches-build-fix.patch
memcg-memswap-controller-kconfig.patch
memcg-swap-cgroup-for-remembering-usage.patch
memcg-memswap-controller-core.patch
memcg-memswap-controller-core-make-resize-limit-hold-mutex.patch
memcg-memswap-controller-core-swapcache-fixes.patch
memcg-synchronized-lru.patch
memcg-add-mem_cgroup_disabled.patch
memcg-add-mem_cgroup_disabled-fix.patch
memory-cgroup-hierarchy-documentation-v4.patch
memory-cgroup-resource-counters-for-hierarchy-v4.patch
memory-cgroup-resource-counters-for-hierarchy-v4-checkpatch-fixes.patch
memory-cgroup-hierarchical-reclaim-v4.patch
memory-cgroup-hierarchical-reclaim-v4-checkpatch-fixes.patch
memory-cgroup-hierarchical-reclaim-v4-fix-for-hierarchical-reclaim.patch
memory-cgroup-hierarchy-feature-selector-v4.patch
memory-cgroup-hierarchy-feature-selector-v4-fix.patch
memcontrol-rcu_read_lock-to-protect-mm_match_cgroup.patch
memcg-avoid-unnecessary-system-wide-oom-killer.patch
memcg-avoid-unnecessary-system-wide-oom-killer-fix.patch
memcg-fix-reclaim-result-checks.patch
memcg-revert-gfp-mask-fix.patch
memcg-check-group-leader-fix.patch
memcg-memoryswap-controller-fix-limit-check.patch
memcg-swapout-refcnt-fix.patch
memcg-hierarchy-avoid-unnecessary-reclaim.patch
inactive_anon_is_low-move-to-vmscan.patch
mm-introduce-zone_reclaim-struct.patch
mm-add-zone-nr_pages-helper-function.patch
memcg-add-null-check-to-page_cgroup_zoneinfo.patch
memcg-add-inactive_anon_is_low.patch
memcg-add-mem_cgroup_zone_nr_pages.patch
memcg-add-zone_reclaim_stat.patch
memcg-show-reclaim-stat.patch
memcg-rename-scan-global-lru.patch
memcg-protect-prev_priority.patch
memcg-swappiness.patch
memcg-fix-calclation-of-active_ratio.patch
memcg-fix-calclation-of-active_ratio-build-error-fix.patch
memcg-show-real-limit-under-hierarchy-mode.patch
memcg-explain-details-and-test-document.patch
memcg-explain-details-and-test-document-fix.patch
memcg-dont-trigger-oom-at-page-migration.patch
memcg-remove-mem_cgroup_try_charge.patch
memcg-avoid-dead-lock-caused-by-race-between-oom-and-cpuset_attach.patch
memcg-change-try_to_free_pages-to-hierarchical_reclaim.patch
memcg-fix-swap-accounting-leak-v3.patch
memcg-fix-swap-accounting-leak-doc-fix.patch
memcg-fix-double-free-and-make-refcnt-sane.patch
memcg-use-css_tryget-in-memcg.patch
cgroups-add-a-per-subsystem-hierarchy_mutex.patch
cgroups-use-hierarchy_mutex-in-memory-controller.patch
cgroups-add-css_tryget.patch
cpuset-rcu_read_lock-to-protect-task_cs.patch
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