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mm: fix vm-scalability regression in cgroup-aware workingset code 

Commit 23047a96d7 ("mm: workingset: per-cgroup cache thrash
detection") added a page->mem_cgroup lookup to the cache eviction,
refault, and activation paths, as well as locking to the activation
path, and the vm-scalability tests showed a regression of -23%.

While the test in question is an artificial worst-case scenario that
doesn't occur in real workloads - reading two sparse files in parallel
at full CPU speed just to hammer the LRU paths - there is still some
optimizations that can be done in those paths.

Inline the lookup functions to eliminate calls.  Also, page->mem_cgroup
doesn't need to be stabilized when counting an activation; we merely
need to hold the RCU lock to prevent the memcg from being freed.

This cuts down on overhead quite a bit:

23047a96d7 063f6715e77a7be5770d6081fe
---------------- --------------------------
         %stddev     %change         %stddev
             \          |                \
  21621405 +- 0%     +11.3%   24069657 +- 2%  vm-scalability.throughput

[linux@roeck-us.net: drop unnecessary include file]
[hannes@cmpxchg.org: add WARN_ON_ONCE()s]
  Link: http://lkml.kernel.org/r/20160707194024.GA26580@cmpxchg.org
Link: http://lkml.kernel.org/r/20160624175101.GA3024@cmpxchg.org
Reported-by: Ye Xiaolong <xiaolong.ye@intel.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2016-07-28 15:45:10 -07:00 committed by Linus Torvalds
parent 400bc7fd4f
commit 55779ec759
4 changed files with 58 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
include/linux/memcontrol.h
View File

@ -314,7 +314,48 @@ void mem_cgroup_uncharge_list(struct list_head *page_list);
void mem_cgroup_migrate(struct page *oldpage, struct page *newpage);
struct lruvec *mem_cgroup_zone_lruvec(struct zone *, struct mem_cgroup *);
static inline struct mem_cgroup_per_zone *
mem_cgroup_zone_zoneinfo(struct mem_cgroup *memcg, struct zone *zone)
{
int nid = zone_to_nid(zone);
int zid = zone_idx(zone);
return &memcg->nodeinfo[nid]->zoneinfo[zid];
}
/**
* mem_cgroup_zone_lruvec - get the lru list vector for a zone and memcg
* @zone: zone of the wanted lruvec
* @memcg: memcg of the wanted lruvec
*
* Returns the lru list vector holding pages for the given @zone and
* @mem. This can be the global zone lruvec, if the memory controller
* is disabled.
*/
static inline struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
struct mem_cgroup *memcg)
{
struct mem_cgroup_per_zone *mz;
struct lruvec *lruvec;
if (mem_cgroup_disabled()) {
lruvec = &zone->lruvec;
goto out;
}
mz = mem_cgroup_zone_zoneinfo(memcg, zone);
lruvec = &mz->lruvec;
out:
/*
* Since a node can be onlined after the mem_cgroup was created,
* we have to be prepared to initialize lruvec->zone here;
* and if offlined then reonlined, we need to reinitialize it.
*/
if (unlikely(lruvec->zone != zone))
lruvec->zone = zone;
return lruvec;
}
struct lruvec *mem_cgroup_page_lruvec(struct page *, struct zone *);
bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg);

10
include/linux/mm.h
View File

@ -973,11 +973,21 @@ static inline struct mem_cgroup *page_memcg(struct page *page)
{
return page->mem_cgroup;
}
static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
{
WARN_ON_ONCE(!rcu_read_lock_held());
return READ_ONCE(page->mem_cgroup);
}
#else
static inline struct mem_cgroup *page_memcg(struct page *page)
{
return NULL;
}
static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
{
WARN_ON_ONCE(!rcu_read_lock_held());
return NULL;
}
#endif
/*

42
mm/memcontrol.c
View File

@ -323,15 +323,6 @@ EXPORT_SYMBOL(memcg_kmem_enabled_key);
#endif /* !CONFIG_SLOB */
static struct mem_cgroup_per_zone *
mem_cgroup_zone_zoneinfo(struct mem_cgroup *memcg, struct zone *zone)
{
int nid = zone_to_nid(zone);
int zid = zone_idx(zone);
return &memcg->nodeinfo[nid]->zoneinfo[zid];
}
/**
* mem_cgroup_css_from_page - css of the memcg associated with a page
* @page: page of interest
@ -943,39 +934,6 @@ static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg)
iter != NULL; \
iter = mem_cgroup_iter(NULL, iter, NULL))
/**
* mem_cgroup_zone_lruvec - get the lru list vector for a zone and memcg
* @zone: zone of the wanted lruvec
* @memcg: memcg of the wanted lruvec
*
* Returns the lru list vector holding pages for the given @zone and
* @mem. This can be the global zone lruvec, if the memory controller
* is disabled.
*/
struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
struct mem_cgroup *memcg)
{
struct mem_cgroup_per_zone *mz;
struct lruvec *lruvec;
if (mem_cgroup_disabled()) {
lruvec = &zone->lruvec;
goto out;
}
mz = mem_cgroup_zone_zoneinfo(memcg, zone);
lruvec = &mz->lruvec;
out:
/*
* Since a node can be onlined after the mem_cgroup was created,
* we have to be prepared to initialize lruvec->zone here;
* and if offlined then reonlined, we need to reinitialize it.
*/
if (unlikely(lruvec->zone != zone))
lruvec->zone = zone;
return lruvec;
}
/**
* mem_cgroup_page_lruvec - return lruvec for isolating/putting an LRU page
* @page: the page

10
mm/workingset.c
View File

@ -305,9 +305,10 @@ bool workingset_refault(void *shadow)
*/
void workingset_activation(struct page *page)
{
struct mem_cgroup *memcg;
struct lruvec *lruvec;
lock_page_memcg(page);
rcu_read_lock();
/*
* Filter non-memcg pages here, e.g. unmap can call
* mark_page_accessed() on VDSO pages.
@ -315,12 +316,13 @@ void workingset_activation(struct page *page)
* XXX: See workingset_refault() - this should return
* root_mem_cgroup even for !CONFIG_MEMCG.
*/
if (!mem_cgroup_disabled() && !page_memcg(page))
memcg = page_memcg_rcu(page);
if (!mem_cgroup_disabled() && !memcg)
goto out;
lruvec = mem_cgroup_zone_lruvec(page_zone(page), page_memcg(page));
lruvec = mem_cgroup_zone_lruvec(page_zone(page), memcg);
atomic_long_inc(&lruvec->inactive_age);
out:
unlock_page_memcg(page);
rcu_read_unlock();
}
/*