2011/4/15 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>:
> On Thu, 14 Apr 2011 15:54:26 -0700
> Ying Han <yinghan@xxxxxxxxxx> wrote:
>
>> After reclaiming each node per memcg, it checks mem_cgroup_watermark_ok()
>> and breaks the priority loop if it returns true. The per-memcg zone will
>> be marked as "unreclaimable" if the scanning rate is much greater than the
>> reclaiming rate on the per-memcg LRU. The bit is cleared when there is a
>> page charged to the memcg being freed. Kswapd breaks the priority loop if
>> all the zones are marked as "unreclaimable".
>>
>> changelog v4..v3:
>> 1. split off from the per-memcg background reclaim patch in V3.
>>
>> Signed-off-by: Ying Han <yinghan@xxxxxxxxxx>
>> ---
>> include/linux/memcontrol.h | 30 ++++++++++++++
>> include/linux/swap.h | 2 +
>> mm/memcontrol.c | 96 ++++++++++++++++++++++++++++++++++++++++++++
>> mm/vmscan.c | 19 +++++++++
>> 4 files changed, 147 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
>> index d4ff7f2..a8159f5 100644
>> --- a/include/linux/memcontrol.h
>> +++ b/include/linux/memcontrol.h
>> @@ -155,6 +155,12 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
>> unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
>> gfp_t gfp_mask);
>> u64 mem_cgroup_get_limit(struct mem_cgroup *mem);
>> +void mem_cgroup_clear_unreclaimable(struct mem_cgroup *mem, struct page *page);
>> +bool mem_cgroup_zone_reclaimable(struct mem_cgroup *mem, int nid, int zid);
>> +bool mem_cgroup_mz_unreclaimable(struct mem_cgroup *mem, struct zone *zone);
>> +void mem_cgroup_mz_set_unreclaimable(struct mem_cgroup *mem, struct zone *zone);
>> +void mem_cgroup_mz_pages_scanned(struct mem_cgroup *mem, struct zone* zone,
>> + unsigned long nr_scanned);
>>
>> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> void mem_cgroup_split_huge_fixup(struct page *head, struct page *tail);
>> @@ -345,6 +351,25 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
>> {
>> }
>>
>> +static inline void mem_cgroup_mz_pages_scanned(struct mem_cgroup *mem,
>> + struct zone *zone,
>> + unsigned long nr_scanned)
>> +{
>> +}
>> +
>> +static inline void mem_cgroup_clear_unreclaimable(struct page *page,
>> + struct zone *zone)
>> +{
>> +}
>> +static inline void mem_cgroup_mz_set_unreclaimable(struct mem_cgroup *mem,
>> + struct zone *zone)
>> +{
>> +}
>> +static inline bool mem_cgroup_mz_unreclaimable(struct mem_cgroup *mem,
>> + struct zone *zone)
>> +{
>> +}
>> +
>> static inline
>> unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
>> gfp_t gfp_mask)
>> @@ -363,6 +388,11 @@ static inline void mem_cgroup_split_huge_fixup(struct page *head,
>> {
>> }
>>
>> +static inline bool mem_cgroup_zone_reclaimable(struct mem_cgroup *mem, int nid,
>> + int zid)
>> +{
>> + return false;
>> +}
>> #endif /* CONFIG_CGROUP_MEM_CONT */
>>
>> #if !defined(CONFIG_CGROUP_MEM_RES_CTLR) || !defined(CONFIG_DEBUG_VM)
>> diff --git a/include/linux/swap.h b/include/linux/swap.h
>> index 17e0511..319b800 100644
>> --- a/include/linux/swap.h
>> +++ b/include/linux/swap.h
>> @@ -160,6 +160,8 @@ enum {
>> SWP_SCANNING = (1 << 8), /* refcount in scan_swap_map */
>> };
>>
>> +#define ZONE_RECLAIMABLE_RATE 6
>> +
>> #define SWAP_CLUSTER_MAX 32
>> #define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index e22351a..da6a130 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -133,7 +133,10 @@ struct mem_cgroup_per_zone {
>> bool on_tree;
>> struct mem_cgroup *mem; /* Back pointer, we cannot */
>> /* use container_of */
>> + unsigned long pages_scanned; /* since last reclaim */
>> + bool all_unreclaimable; /* All pages pinned */
>> };
>> +
>> /* Macro for accessing counter */
>> #define MEM_CGROUP_ZSTAT(mz, idx) ((mz)->count[(idx)])
>>
>> @@ -1135,6 +1138,96 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page)
>> return &mz->reclaim_stat;
>> }
>>
>> +static unsigned long mem_cgroup_zone_reclaimable_pages(
>> + struct mem_cgroup_per_zone *mz)
>> +{
>> + int nr;
>> + nr = MEM_CGROUP_ZSTAT(mz, LRU_ACTIVE_FILE) +
>> + MEM_CGROUP_ZSTAT(mz, LRU_INACTIVE_FILE);
>> +
>> + if (nr_swap_pages > 0)
>> + nr += MEM_CGROUP_ZSTAT(mz, LRU_ACTIVE_ANON) +
>> + MEM_CGROUP_ZSTAT(mz, LRU_INACTIVE_ANON);
>> +
>> + return nr;
>> +}
>> +
>> +void mem_cgroup_mz_pages_scanned(struct mem_cgroup *mem, struct zone* zone,
>> + unsigned long nr_scanned)
>> +{
>> + struct mem_cgroup_per_zone *mz = NULL;
>> + int nid = zone_to_nid(zone);
>> + int zid = zone_idx(zone);
>> +
>> + if (!mem)
>> + return;
>> +
>> + mz = mem_cgroup_zoneinfo(mem, nid, zid);
>> + if (mz)
>> + mz->pages_scanned += nr_scanned;
>> +}
>> +
>> +bool mem_cgroup_zone_reclaimable(struct mem_cgroup *mem, int nid, int zid)
>> +{
>> + struct mem_cgroup_per_zone *mz = NULL;
>> +
>> + if (!mem)
>> + return 0;
>> +
>> + mz = mem_cgroup_zoneinfo(mem, nid, zid);
>> + if (mz)
>> + return mz->pages_scanned <
>> + mem_cgroup_zone_reclaimable_pages(mz) *
>> + ZONE_RECLAIMABLE_RATE;
>> + return 0;
>> +}
>> +
>> +bool mem_cgroup_mz_unreclaimable(struct mem_cgroup *mem, struct zone *zone)
>> +{
>> + struct mem_cgroup_per_zone *mz = NULL;
>> + int nid = zone_to_nid(zone);
>> + int zid = zone_idx(zone);
>> +
>> + if (!mem)
>> + return false;
>> +
>> + mz = mem_cgroup_zoneinfo(mem, nid, zid);
>> + if (mz)
>> + return mz->all_unreclaimable;
>> +
>> + return false;
>> +}
>> +
>> +void mem_cgroup_mz_set_unreclaimable(struct mem_cgroup *mem, struct zone *zone)
>> +{
>> + struct mem_cgroup_per_zone *mz = NULL;
>> + int nid = zone_to_nid(zone);
>> + int zid = zone_idx(zone);
>> +
>> + if (!mem)
>> + return;
>> +
>> + mz = mem_cgroup_zoneinfo(mem, nid, zid);
>> + if (mz)
>> + mz->all_unreclaimable = true;
>> +}
>> +
>> +void mem_cgroup_clear_unreclaimable(struct mem_cgroup *mem, struct page *page)
>> +{
>> + struct mem_cgroup_per_zone *mz = NULL;
>> +
>> + if (!mem)
>> + return;
>> +
>> + mz = page_cgroup_zoneinfo(mem, page);
>> + if (mz) {
>> + mz->pages_scanned = 0;
>> + mz->all_unreclaimable = false;
>> + }
>> +
>> + return;
>> +}
>> +
>> unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
>> struct list_head *dst,
>> unsigned long *scanned, int order,
>> @@ -2801,6 +2894,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
>> * special functions.
>> */
>>
>> + mem_cgroup_clear_unreclaimable(mem, page);
>
> Hmm, this will easily cause cache ping-pong. (free_page() clears it after taking
> zone->lock....in batched manner.)
>
> Could you consider a way to make this low cost ?
>
> One way is using memcg_check_event() with some low event trigger.
> Second way is usign memcg_batch.
> In many case, we can expect a chunk of free pages are from the same zone.
> Then, add a new member to batch_memcg as
>
> struct memcg_batch_info {
> .....
> struct zone *zone; # a zone page is last uncharged.
> ...
> }
>
> Then,
> ==
> static void mem_cgroup_do_uncharge(struct mem_cgroup *mem,
> unsigned int nr_pages,
> + struct page *page,
> const enum charge_type ctype)
> {
> struct memcg_batch_info *batch = NULL;
> .....
>
> if (batch->zone != page_zone(page)) {
> mem_cgroup_clear_unreclaimable(mem, page);
> }
> direct_uncharge:
> mem_cgroup_clear_unreclaimable(mem, page);
> ....
> }
> ==
>
> This will reduce overhead dramatically.
>
Excuse me but I don't quite understand this part, IMHO this is to
avoid call mem_cgroup_clear_unreclaimable() against each single page
during a munmap()/free_pages() including many pages to free, which is
unnecessary because the zone will turn into 'reclaimable' at the first
page uncharged.
Then why can't we just say,
if (mem_cgroup_zoneinfo(mem, page_to_nid(page),
page_zonenum(page))->all_unreclaimable) {
mem_cgroup_clear_unreclaimable(mem, page);
}
--
Thanks,
Zhu Yanhai
>
>
>> unlock_page_cgroup(pc);
>> /*
>> * even after unlock, we have mem->res.usage here and this memcg
>> @@ -4569,6 +4663,8 @@ static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
>> mz->usage_in_excess = 0;
>> mz->on_tree = false;
>> mz->mem = mem;
>> + mz->pages_scanned = 0;
>> + mz->all_unreclaimable = false;
>> }
>> return 0;
>> }
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index b8345d2..c081112 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1414,6 +1414,9 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>> ISOLATE_BOTH : ISOLATE_INACTIVE,
>> zone, sc->mem_cgroup,
>> 0, file);
>> +
>> + mem_cgroup_mz_pages_scanned(sc->mem_cgroup, zone, nr_scanned);
>> +
>> /*
>> * mem_cgroup_isolate_pages() keeps track of
>> * scanned pages on its own.
>> @@ -1533,6 +1536,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
>> * mem_cgroup_isolate_pages() keeps track of
>> * scanned pages on its own.
>> */
>> + mem_cgroup_mz_pages_scanned(sc->mem_cgroup, zone, pgscanned);
>> }
>>
>> reclaim_stat->recent_scanned[file] += nr_taken;
>> @@ -2648,6 +2652,7 @@ static void balance_pgdat_node(pg_data_t *pgdat, int order,
>> unsigned long total_scanned = 0;
>> struct mem_cgroup *mem_cont = sc->mem_cgroup;
>> int priority = sc->priority;
>> + int nid = pgdat->node_id;
>>
>> /*
>> * Now scan the zone in the dma->highmem direction, and we scan
>> @@ -2664,10 +2669,20 @@ static void balance_pgdat_node(pg_data_t *pgdat, int order,
>> if (!populated_zone(zone))
>> continue;
>>
>> + if (mem_cgroup_mz_unreclaimable(mem_cont, zone) &&
>> + priority != DEF_PRIORITY)
>> + continue;
>> +
>> sc->nr_scanned = 0;
>> shrink_zone(priority, zone, sc);
>> total_scanned += sc->nr_scanned;
>>
>> + if (mem_cgroup_mz_unreclaimable(mem_cont, zone))
>> + continue;
>> +
>> + if (!mem_cgroup_zone_reclaimable(mem_cont, nid, i))
>> + mem_cgroup_mz_set_unreclaimable(mem_cont, zone);
>> +
>> /*
>> * If we've done a decent amount of scanning and
>> * the reclaim ratio is low, start doing writepage
>> @@ -2752,6 +2767,10 @@ loop_again:
>>
>> if (!populated_zone(zone))
>> continue;
>> +
>> + if (!mem_cgroup_mz_unreclaimable(mem_cont,
>> + zone))
>> +
>
> Ah, okay. this will work.
>
> Thanks,
> -Kame
>
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