Re: [PATCH 3/7] memcg: add memory.scan_stat
From: Ying Han
Date: Fri Jun 17 2011 - 18:04:30 EST
On Wed, Jun 15, 2011 at 8:53 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> From e08990dd9ada13cf236bec1ef44b207436434b8e Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> Date: Wed, 15 Jun 2011 14:11:01 +0900
> Subject: [PATCH 3/7] memcg: add memory.scan_stat
>
> commit log of commit 0ae5e89 " memcg: count the soft_limit reclaim in..."
> says it adds scanning stats to memory.stat file. But it doesn't because
> we considered we needed to make a concensus for such new APIs.
>
> This patch is a trial to add memory.scan_stat. This shows
> - the number of scanned pages
> - the number of recleimed pages
> - the number of elaplsed time (including sleep/pause time)
> for both of direct/soft reclaim and shrinking caused by changing limit
> or force_empty.
>
> The biggest difference with oringinal Ying's one is that this file
> can be reset by some write, as
>
> # echo 0 ...../memory.scan_stat
>
> [kamezawa@bluextal ~]$ cat /cgroup/memory/A/memory.scan_stat
> scanned_pages_by_limit 358470
> freed_pages_by_limit 180795
> elapsed_ns_by_limit 21629927
> scanned_pages_by_system 0
> freed_pages_by_system 0
> elapsed_ns_by_system 0
> scanned_pages_by_shrink 76646
> freed_pages_by_shrink 38355
> elappsed_ns_by_shrink 31990670
> total_scanned_pages_by_limit 358470
> total_freed_pages_by_limit 180795
> total_elapsed_ns_by_hierarchical 216299275
> total_scanned_pages_by_system 0
> total_freed_pages_by_system 0
> total_elapsed_ns_by_system 0
> total_scanned_pages_by_shrink 76646
> total_freed_pages_by_shrink 38355
> total_elapsed_ns_by_shrink 31990670
>
> total_xxxx is for hierarchy management.
>
> This will be useful for further memcg developments and need to be
> developped before we do some complicated rework on LRU/softlimit
> management.
Agreed. Actually we are also looking into adding a per-memcg API for
adding visibility of
page reclaim path. It would be helpful for us to settle w/ the API first.
I am not a fan of names, but how about
"/dev/cgroup/memory/memory.reclaim_stat" ?
>
> Now, scan/free/elapsed_by_system is incomplete but future works of
> Johannes at el. will fill remaining information and then, we can
> look into problems of isolation between memcgs.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
> Documentation/cgroups/memory.txt | 33 +++++++++
> include/linux/memcontrol.h | 16 ++++
> include/linux/swap.h | 6 -
> mm/memcontrol.c | 135 +++++++++++++++++++++++++++++++++++++--
> mm/vmscan.c | 27 ++++++-
> 5 files changed, 199 insertions(+), 18 deletions(-)
>
> Index: mmotm-0615/Documentation/cgroups/memory.txt
> ===================================================================
> --- mmotm-0615.orig/Documentation/cgroups/memory.txt
> +++ mmotm-0615/Documentation/cgroups/memory.txt
> @@ -380,7 +380,7 @@ will be charged as a new owner of it.
>
> 5.2 stat file
>
> -memory.stat file includes following statistics
> +5.2.1 memory.stat file includes following statistics
>
> # per-memory cgroup local status
> cache - # of bytes of page cache memory.
> @@ -438,6 +438,37 @@ Note:
> file_mapped is accounted only when the memory cgroup is owner of page
> cache.)
>
> +5.2.2 memory.scan_stat
> +
> +memory.scan_stat includes statistics information for memory scanning and
> +freeing, reclaiming. The statistics shows memory scanning information since
> +memory cgroup creation and can be reset to 0 by writing 0 as
> +
> + #echo 0 > ../memory.scan_stat
> +
> +This file contains following statistics.
> +
> +scanned_pages_by_limit - # of scanned pages at hitting limit.
> +freed_pages_by_limit - # of freed pages at hitting limit.
How those stats different from Johannes's patch? I feel we should keep
them into this API instead of memory.stat
"pgscan_direct_limit"
"pgreclaim_direct_limit"
> +elapsed_ns_by_limit - nano sec of elappsed time at LRU scan at
> + hitting limit.(this includes sleep time.)
> +
> +scanned_pages_by_system - # of scanned pages by the kernel.
> + (Now, this value means global memory reclaim
> + caused by system memory shortage with a hint
> + of softlimit. "No soft limit" case will be
> + supported in future.)
> +freed_pages_by_system - # of freed pages by the kernel.
The same for the following which I assume the same meaning with:
"pgscan_direct_hierarchy"
"pgreclaim_direct_hierarchy"
> +elapsed_ns_by_system - nano sec of elappsed time by kernel.
> +
> +scanned_pages_by_shrink - # of scanned pages by shrinking.
> + (i.e. changes of limit, force_empty, etc.)
> +freed_pages_by_shrink - # of freed pages by shirkining.
So those stats are not included in the ones above?
--Ying
> +elappsed_ns_by_shrink - nano sec of elappsed time at shrinking.
> +
> +total_xxx includes the statistics of children scanning caused by the cgroup.
> +
> +
> 5.3 swappiness
>
> Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only.
> Index: mmotm-0615/include/linux/memcontrol.h
> ===================================================================
> --- mmotm-0615.orig/include/linux/memcontrol.h
> +++ mmotm-0615/include/linux/memcontrol.h
> @@ -120,6 +120,22 @@ struct zone_reclaim_stat*
> mem_cgroup_get_reclaim_stat_from_page(struct page *page);
> extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
> struct task_struct *p);
> +struct memcg_scanrecord {
> + struct mem_cgroup *mem; /* scanend memory cgroup */
> + struct mem_cgroup *root; /* scan target hierarchy root */
> + int context; /* scanning context (see memcontrol.c) */
> + unsigned long nr_scanned; /* the number of scanned pages */
> + unsigned long nr_freed; /* the number of freed pages */
> + unsigned long elappsed; /* nsec of time elapsed while scanning */
> +};
> +
> +extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
> + gfp_t gfp_mask, bool noswap,
> + struct memcg_scanrecord *rec);
> +extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
> + gfp_t gfp_mask, bool noswap,
> + struct zone *zone,
> + struct memcg_scanrecord *rec);
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> extern int do_swap_account;
> Index: mmotm-0615/include/linux/swap.h
> ===================================================================
> --- mmotm-0615.orig/include/linux/swap.h
> +++ mmotm-0615/include/linux/swap.h
> @@ -253,12 +253,6 @@ static inline void lru_cache_add_file(st
> /* linux/mm/vmscan.c */
> extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
> gfp_t gfp_mask, nodemask_t *mask);
> -extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
> - gfp_t gfp_mask, bool noswap);
> -extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
> - gfp_t gfp_mask, bool noswap,
> - struct zone *zone,
> - unsigned long *nr_scanned);
> extern int __isolate_lru_page(struct page *page, int mode, int file);
> extern unsigned long shrink_all_memory(unsigned long nr_pages);
> extern int vm_swappiness;
> Index: mmotm-0615/mm/memcontrol.c
> ===================================================================
> --- mmotm-0615.orig/mm/memcontrol.c
> +++ mmotm-0615/mm/memcontrol.c
> @@ -203,6 +203,57 @@ struct mem_cgroup_eventfd_list {
> static void mem_cgroup_threshold(struct mem_cgroup *mem);
> static void mem_cgroup_oom_notify(struct mem_cgroup *mem);
>
> +enum {
> + SCAN_BY_LIMIT,
> + FREED_BY_LIMIT,
> + ELAPSED_BY_LIMIT,
> +
> + SCAN_BY_SYSTEM,
> + FREED_BY_SYSTEM,
> + ELAPSED_BY_SYSTEM,
> +
> + SCAN_BY_SHRINK,
> + FREED_BY_SHRINK,
> + ELAPSED_BY_SHRINK,
> + NR_SCANSTATS,
> +};
> +#define __FREED (1)
> +#define __ELAPSED (2)
> +
> +struct scanstat {
> + spinlock_t lock;
> + unsigned long stats[NR_SCANSTATS]; /* local statistics */
> + unsigned long totalstats[NR_SCANSTATS]; /* hierarchical */
> +};
> +
> +const char *scanstat_string[NR_SCANSTATS] = {
> + "scanned_pages_by_limit",
> + "freed_pages_by_limit",
> + "elapsed_ns_by_limit",
> +
> + "scanned_pages_by_system",
> + "freed_pages_by_system",
> + "elapsed_ns_by_system",
> +
> + "scanned_pages_by_shrink",
> + "freed_pages_by_shrink",
> + "elappsed_ns_by_shrink",
> +};
> +
> +const char *total_scanstat_string[NR_SCANSTATS] = {
> + "total_scanned_pages_by_limit",
> + "total_freed_pages_by_limit",
> + "total_elapsed_ns_by_hierarchical",
> +
> + "total_scanned_pages_by_system",
> + "total_freed_pages_by_system",
> + "total_elapsed_ns_by_system",
> +
> + "total_scanned_pages_by_shrink",
> + "total_freed_pages_by_shrink",
> + "total_elapsed_ns_by_shrink",
> +};
> +
> /*
> * The memory controller data structure. The memory controller controls both
> * page cache and RSS per cgroup. We would eventually like to provide
> @@ -264,7 +315,8 @@ struct mem_cgroup {
>
> /* For oom notifier event fd */
> struct list_head oom_notify;
> -
> + /* For recording LRU-scan statistics */
> + struct scanstat scanstat;
> /*
> * Should we move charges of a task when a task is moved into this
> * mem_cgroup ? And what type of charges should we move ?
> @@ -1634,6 +1686,28 @@ int mem_cgroup_select_victim_node(struct
> }
> #endif
>
> +
> +
> +static void mem_cgroup_record_scanstat(struct memcg_scanrecord *rec)
> +{
> + struct mem_cgroup *mem;
> + int context = rec->context;
> +
> + mem = rec->mem;
> + spin_lock(&mem->scanstat.lock);
> + mem->scanstat.stats[context] += rec->nr_scanned;
> + mem->scanstat.stats[context + __FREED] += rec->nr_freed;
> + mem->scanstat.stats[context + __ELAPSED] += rec->elappsed;
> + spin_unlock(&mem->scanstat.lock);
> +
> + mem = rec->root;
> + spin_lock(&mem->scanstat.lock);
> + mem->scanstat.totalstats[context] += rec->nr_scanned;
> + mem->scanstat.totalstats[context + __FREED] += rec->nr_freed;
> + mem->scanstat.totalstats[context + __ELAPSED] += rec->elappsed;
> + spin_unlock(&mem->scanstat.lock);
> +}
> +
> /*
> * Scan the hierarchy if needed to reclaim memory. We remember the last child
> * we reclaimed from, so that we don't end up penalizing one child extensively
> @@ -1659,8 +1733,8 @@ static int mem_cgroup_hierarchical_recla
> bool shrink = reclaim_options & MEM_CGROUP_RECLAIM_SHRINK;
> bool check_soft = reclaim_options & MEM_CGROUP_RECLAIM_SOFT;
> unsigned long excess;
> - unsigned long nr_scanned;
> int visit;
> + struct memcg_scanrecord rec;
>
> excess = res_counter_soft_limit_excess(&root_mem->res) >> PAGE_SHIFT;
>
> @@ -1668,6 +1742,15 @@ static int mem_cgroup_hierarchical_recla
> if (!check_soft && root_mem->memsw_is_minimum)
> noswap = true;
>
> + if (shrink)
> + rec.context = SCAN_BY_SHRINK;
> + else if (check_soft)
> + rec.context = SCAN_BY_SYSTEM;
> + else
> + rec.context = SCAN_BY_LIMIT;
> +
> + rec.root = root_mem;
> +
> again:
> if (!shrink) {
> visit = 0;
> @@ -1695,14 +1778,19 @@ again:
> css_put(&victim->css);
> continue;
> }
> + rec.mem = victim;
> + rec.nr_scanned = 0;
> + rec.nr_freed = 0;
> + rec.elappsed = 0;
> /* we use swappiness of local cgroup */
> if (check_soft) {
> ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,
> - noswap, zone, &nr_scanned);
> - *total_scanned += nr_scanned;
> + noswap, zone, &rec);
> + *total_scanned += rec.nr_scanned;
> } else
> ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
> - noswap);
> + noswap, &rec);
> + mem_cgroup_record_scanstat(&rec);
> css_put(&victim->css);
>
> total += ret;
> @@ -3757,7 +3845,8 @@ try_to_free:
> ret = -EINTR;
> goto out;
> }
> - progress = try_to_free_mem_cgroup_pages(mem, GFP_KERNEL, false);
> + progress = try_to_free_mem_cgroup_pages(mem,
> + GFP_KERNEL, false, NULL);
> if (!progress) {
> nr_retries--;
> /* maybe some writeback is necessary */
> @@ -4599,6 +4688,34 @@ static int mem_control_numa_stat_open(st
> }
> #endif /* CONFIG_NUMA */
>
> +static int mem_cgroup_scan_stat_read(struct cgroup *cgrp,
> + struct cftype *cft,
> + struct cgroup_map_cb *cb)
> +{
> + struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
> + int i;
> +
> + for (i = 0; i < NR_SCANSTATS; i++)
> + cb->fill(cb, scanstat_string[i], mem->scanstat.stats[i]);
> + for (i = 0; i < NR_SCANSTATS; i++)
> + cb->fill(cb, total_scanstat_string[i],
> + mem->scanstat.totalstats[i]);
> + return 0;
> +}
> +
> +static int mem_cgroup_reset_scan_stat(struct cgroup *cgrp,
> + unsigned int event)
> +{
> + struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
> +
> + spin_lock(&mem->scanstat.lock);
> + memset(&mem->scanstat.stats, 0, sizeof(mem->scanstat.stats));
> + memset(&mem->scanstat.totalstats, 0, sizeof(mem->scanstat.totalstats));
> + spin_unlock(&mem->scanstat.lock);
> + return 0;
> +}
> +
> +
> static struct cftype mem_cgroup_files[] = {
> {
> .name = "usage_in_bytes",
> @@ -4669,6 +4786,11 @@ static struct cftype mem_cgroup_files[]
> .mode = S_IRUGO,
> },
> #endif
> + {
> + .name = "scan_stat",
> + .read_map = mem_cgroup_scan_stat_read,
> + .trigger = mem_cgroup_reset_scan_stat,
> + },
> };
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> @@ -4932,6 +5054,7 @@ mem_cgroup_create(struct cgroup_subsys *
> atomic_set(&mem->refcnt, 1);
> mem->move_charge_at_immigrate = 0;
> mutex_init(&mem->thresholds_lock);
> + spin_lock_init(&mem->scanstat.lock);
> return &mem->css;
> free_out:
> __mem_cgroup_free(mem);
> Index: mmotm-0615/mm/vmscan.c
> ===================================================================
> --- mmotm-0615.orig/mm/vmscan.c
> +++ mmotm-0615/mm/vmscan.c
> @@ -2199,9 +2199,9 @@ unsigned long try_to_free_pages(struct z
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR
>
> unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
> - gfp_t gfp_mask, bool noswap,
> - struct zone *zone,
> - unsigned long *nr_scanned)
> + gfp_t gfp_mask, bool noswap,
> + struct zone *zone,
> + struct memcg_scanrecord *rec)
> {
> struct scan_control sc = {
> .nr_scanned = 0,
> @@ -2213,6 +2213,7 @@ unsigned long mem_cgroup_shrink_node_zon
> .order = 0,
> .mem_cgroup = mem,
> };
> + unsigned long start, end;
>
> sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
> (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
> @@ -2221,6 +2222,7 @@ unsigned long mem_cgroup_shrink_node_zon
> sc.may_writepage,
> sc.gfp_mask);
>
> + start = sched_clock();
> /*
> * NOTE: Although we can get the priority field, using it
> * here is not a good idea, since it limits the pages we can scan.
> @@ -2229,19 +2231,27 @@ unsigned long mem_cgroup_shrink_node_zon
> * the priority and make it zero.
> */
> shrink_zone(0, zone, &sc);
> + end = sched_clock();
> +
> + if (rec) {
> + rec->nr_scanned += sc.nr_scanned;
> + rec->nr_freed += sc.nr_reclaimed;
> + rec->elappsed += end - start;
> + }
>
> trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
>
> - *nr_scanned = sc.nr_scanned;
> return sc.nr_reclaimed;
> }
>
> unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
> gfp_t gfp_mask,
> - bool noswap)
> + bool noswap,
> + struct memcg_scanrecord *rec)
> {
> struct zonelist *zonelist;
> unsigned long nr_reclaimed;
> + unsigned long start, end;
> int nid;
> struct scan_control sc = {
> .may_writepage = !laptop_mode,
> @@ -2259,6 +2269,7 @@ unsigned long try_to_free_mem_cgroup_pag
> .gfp_mask = sc.gfp_mask,
> };
>
> + start = sched_clock();
> /*
> * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
> * take care of from where we get pages. So the node where we start the
> @@ -2273,6 +2284,12 @@ unsigned long try_to_free_mem_cgroup_pag
> sc.gfp_mask);
>
> nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
> + end = sched_clock();
> + if (rec) {
> + rec->nr_scanned += sc.nr_scanned;
> + rec->nr_freed += sc.nr_reclaimed;
> + rec->elappsed += end - start;
> + }
>
> trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
>
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/