Commit f77f0c75 authored by Kaiyang Zhao's avatar Kaiyang Zhao Committed by Andrew Morton
Browse files

mm,memcg: provide per-cgroup counters for NUMA balancing operations 

The ability to observe the demotion and promotion decisions made by the
kernel on a per-cgroup basis is important for monitoring and tuning
containerized workloads on machines equipped with tiered memory.

Different containers in the system may experience drastically different
memory tiering actions that cannot be distinguished from the global
counters alone.

For example, a container running a workload that has a much hotter memory
accesses will likely see more promotions and fewer demotions, potentially
depriving a colocated container of top tier memory to such an extent that
its performance degrades unacceptably.

For another example, some containers may exhibit longer periods between
data reuse, causing much more numa_hint_faults than numa_pages_migrated. 
In this case, tuning hot_threshold_ms may be appropriate, but the signal
can easily be lost if only global counters are available.

In the long term, we hope to introduce per-cgroup control of promotion and
demotion actions to implement memory placement policies in tiering.

This patch set adds seven counters to memory.stat in a cgroup:
numa_pages_migrated, numa_pte_updates, numa_hint_faults, pgdemote_kswapd,
pgdemote_khugepaged, pgdemote_direct and pgpromote_success.  pgdemote_*
and pgpromote_success are also available in memory.numa_stat.

count_memcg_events_mm() is added to count multiple event occurrences at
once, and get_mem_cgroup_from_folio() is added because we need to get a
reference to the memcg of a folio before it's migrated to track
numa_pages_migrated.  The accounting of PGDEMOTE_* is moved to
shrink_inactive_list() before being changed to per-cgroup.

[kaiyang2@cs.cmu.edu: add documentation of the memcg counters in cgroup-v2.rst]
  Link: https://lkml.kernel.org/r/20240814235122.252309-1-kaiyang2@cs.cmu.edu
Link: https://lkml.kernel.org/r/20240814174227.30639-1-kaiyang2@cs.cmu.edu


Signed-off-by: default avatarKaiyang Zhao <kaiyang2@cs.cmu.edu>
Cc: David Rientjes <rientjes@google.com>
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: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Wei Xu <weixugc@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 78788c3e

Documentation/admin-guide/cgroup-v2.rst

+19 −0
Original line number Diff line number Diff line
@@ -1617,6 +1617,25 @@ The following nested keys are defined. 
		Usually because failed to allocate some continuous swap space

		for the huge page.



	  numa_pages_migrated (npn)

		Number of pages migrated by NUMA balancing.



	  numa_pte_updates (npn)

		Number of pages whose page table entries are modified by

		NUMA balancing to produce NUMA hinting faults on access.



	  numa_hint_faults (npn)

		Number of NUMA hinting faults.



	  pgdemote_kswapd

		Number of pages demoted by kswapd.



	  pgdemote_direct

		Number of pages demoted directly.



	  pgdemote_khugepaged

		Number of pages demoted by khugepaged.



  memory.numa_stat

	A read-only nested-keyed file which exists on non-root cgroups.

include/linux/memcontrol.h

+21 −3
Original line number Diff line number Diff line
@@ -784,6 +784,8 @@ struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm); 


struct mem_cgroup *get_mem_cgroup_from_current(void);



struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio);



struct lruvec *folio_lruvec_lock(struct folio *folio);

struct lruvec *folio_lruvec_lock_irq(struct folio *folio);

struct lruvec *folio_lruvec_lock_irqsave(struct folio *folio,
@@ -1028,8 +1030,8 @@ static inline void count_memcg_folio_events(struct folio *folio, 
		count_memcg_events(memcg, idx, nr);

}



static inline void count_memcg_event_mm(struct mm_struct *mm,

					enum vm_event_item idx)

static inline void count_memcg_events_mm(struct mm_struct *mm,

					enum vm_event_item idx, unsigned long count)

{

	struct mem_cgroup *memcg;
@@ -1039,10 +1041,16 @@ static inline void count_memcg_event_mm(struct mm_struct *mm, 
	rcu_read_lock();

	memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));

	if (likely(memcg))

		count_memcg_events(memcg, idx, 1);

		count_memcg_events(memcg, idx, count);

	rcu_read_unlock();

}



static inline void count_memcg_event_mm(struct mm_struct *mm,

					enum vm_event_item idx)

{

	count_memcg_events_mm(mm, idx, 1);

}



static inline void memcg_memory_event(struct mem_cgroup *memcg,

				      enum memcg_memory_event event)

{
@@ -1262,6 +1270,11 @@ static inline struct mem_cgroup *get_mem_cgroup_from_current(void) 
	return NULL;

}



static inline struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio)

{

	return NULL;

}



static inline

struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *css)

{
@@ -1484,6 +1497,11 @@ static inline void count_memcg_folio_events(struct folio *folio, 
{

}



static inline void count_memcg_events_mm(struct mm_struct *mm,

					enum vm_event_item idx, unsigned long count)

{

}



static inline

void count_memcg_event_mm(struct mm_struct *mm, enum vm_event_item idx)

{

include/linux/vmstat.h

+1 −0
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ struct reclaim_stat { 
	unsigned nr_ref_keep;

	unsigned nr_unmap_fail;

	unsigned nr_lazyfree_fail;

	unsigned nr_demoted;

};



/* Stat data for system wide items */

mm/memcontrol.c

+45 −0
Original line number Diff line number Diff line
@@ -304,6 +304,12 @@ static const unsigned int memcg_node_stat_items[] = { 
#ifdef CONFIG_SWAP

	NR_SWAPCACHE,

#endif

#ifdef CONFIG_NUMA_BALANCING

	PGPROMOTE_SUCCESS,

#endif

	PGDEMOTE_KSWAPD,

	PGDEMOTE_DIRECT,

	PGDEMOTE_KHUGEPAGED,

};



static const unsigned int memcg_stat_items[] = {
@@ -436,6 +442,11 @@ static const unsigned int memcg_vm_event_stat[] = { 
	THP_SWPOUT,

	THP_SWPOUT_FALLBACK,

#endif

#ifdef CONFIG_NUMA_BALANCING

	NUMA_PAGE_MIGRATE,

	NUMA_PTE_UPDATES,

	NUMA_HINT_FAULTS,

#endif

};



#define NR_MEMCG_EVENTS ARRAY_SIZE(memcg_vm_event_stat)
@@ -935,6 +946,24 @@ struct mem_cgroup *get_mem_cgroup_from_current(void) 
	return memcg;

}



/**

 * get_mem_cgroup_from_folio - Obtain a reference on a given folio's memcg.

 * @folio: folio from which memcg should be extracted.

 */

struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio)

{

	struct mem_cgroup *memcg = folio_memcg(folio);



	if (mem_cgroup_disabled())

		return NULL;



	rcu_read_lock();

	if (!memcg || WARN_ON_ONCE(!css_tryget(&memcg->css)))

		memcg = root_mem_cgroup;

	rcu_read_unlock();

	return memcg;

}



/**

 * mem_cgroup_iter - iterate over memory cgroup hierarchy

 * @root: hierarchy root
@@ -1340,6 +1369,13 @@ static const struct memory_stat memory_stats[] = { 
	{ "workingset_restore_anon",	WORKINGSET_RESTORE_ANON		},

	{ "workingset_restore_file",	WORKINGSET_RESTORE_FILE		},

	{ "workingset_nodereclaim",	WORKINGSET_NODERECLAIM		},



	{ "pgdemote_kswapd",		PGDEMOTE_KSWAPD		},

	{ "pgdemote_direct",		PGDEMOTE_DIRECT		},

	{ "pgdemote_khugepaged",	PGDEMOTE_KHUGEPAGED	},

#ifdef CONFIG_NUMA_BALANCING

	{ "pgpromote_success",		PGPROMOTE_SUCCESS	},

#endif

};



/* The actual unit of the state item, not the same as the output unit */
@@ -1364,6 +1400,9 @@ static int memcg_page_state_output_unit(int item) 
	/*

	 * Workingset state is actually in pages, but we export it to userspace

	 * as a scalar count of events, so special case it here.

	 *

	 * Demotion and promotion activities are exported in pages, consistent

	 * with their global counterparts.

	 */

	switch (item) {

	case WORKINGSET_REFAULT_ANON:
@@ -1373,6 +1412,12 @@ static int memcg_page_state_output_unit(int item) 
	case WORKINGSET_RESTORE_ANON:

	case WORKINGSET_RESTORE_FILE:

	case WORKINGSET_NODERECLAIM:

	case PGDEMOTE_KSWAPD:

	case PGDEMOTE_DIRECT:

	case PGDEMOTE_KHUGEPAGED:

#ifdef CONFIG_NUMA_BALANCING

	case PGPROMOTE_SUCCESS:

#endif

		return 1;

	default:

		return memcg_page_state_unit(item);

mm/memory.c

+3 −0
Original line number Diff line number Diff line
@@ -5236,6 +5236,9 @@ int numa_migrate_check(struct folio *folio, struct vm_fault *vmf, 
	vma_set_access_pid_bit(vma);



	count_vm_numa_event(NUMA_HINT_FAULTS);

#ifdef CONFIG_NUMA_BALANCING

	count_memcg_folio_events(folio, NUMA_HINT_FAULTS, 1);

#endif

	if (folio_nid(folio) == numa_node_id()) {

		count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);

		*flags |= TNF_FAULT_LOCAL;