Re: [PATCH 5/7] mm: rework reclaim_stat counters
From: KAMEZAWA Hiroyuki
Date: Fri Mar 02 2012 - 00:29:53 EST
On Wed, 29 Feb 2012 13:15:56 +0400
Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> wrote:
> Currently there is two types of reclaim-stat counters:
> recent_scanned (pages picked from from lru),
> recent_rotated (pages putted back to active lru).
> Reclaimer uses ratio recent_rotated / recent_scanned
> for balancing pressure between file and anon pages.
>
> But if we pick page from lru we can either reclaim it or put it back to lru, thus:
> recent_scanned == recent_rotated[inactive] + recent_rotated[active] + reclaimed
> This can be called "The Law of Conservation of Memory" =)
>
I'm sorry....where is the count for active->incative ?
> Thus recent_rotated counters for each lru list is enough, reclaimed pages can be
> counted as rotatation into inactive lru. After that reclaimer can use this ratio:
> recent_rotated[active] / (recent_rotated[active] + recent_rotated[inactive])
>
> After this patch struct zone_reclaimer_stat has only one array: recent_rotated,
> which is directly indexed by lru list index.
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
I'm sorry if I misunderstand..
Recent_scanned can be update by some logics other than vmscan..
For example, how lru_deactivate_fn() is handled ?
Thanks,
-Kame
> ---
> include/linux/mmzone.h | 11 +++++------
> mm/memcontrol.c | 29 +++++++++++++++++------------
> mm/page_alloc.c | 6 ++----
> mm/swap.c | 26 ++++++++------------------
> mm/vmscan.c | 42 ++++++++++++++++++++++--------------------
> 5 files changed, 54 insertions(+), 60 deletions(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 2fed935..fdcd683 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -137,12 +137,14 @@ enum lru_list {
> LRU_INACTIVE_FILE = LRU_BASE + LRU_FILE,
> LRU_ACTIVE_FILE = LRU_BASE + LRU_FILE + LRU_ACTIVE,
> LRU_UNEVICTABLE,
> - NR_LRU_LISTS
> + NR_LRU_LISTS,
> + NR_EVICTABLE_LRU_LISTS = LRU_UNEVICTABLE,
> };
>
> #define for_each_lru(lru) for (lru = 0; lru < NR_LRU_LISTS; lru++)
>
> -#define for_each_evictable_lru(lru) for (lru = 0; lru <= LRU_ACTIVE_FILE; lru++)
> +#define for_each_evictable_lru(lru) \
> + for (lru = 0; lru < NR_EVICTABLE_LRU_LISTS; lru++)
>
> static inline int is_file_lru(enum lru_list lru)
> {
> @@ -165,11 +167,8 @@ struct zone_reclaim_stat {
> * mem/swap backed and file backed pages are refeferenced.
> * The higher the rotated/scanned ratio, the more valuable
> * that cache is.
> - *
> - * The anon LRU stats live in [0], file LRU stats in [1]
> */
> - unsigned long recent_rotated[2];
> - unsigned long recent_scanned[2];
> + unsigned long recent_rotated[NR_EVICTABLE_LRU_LISTS];
> };
>
> struct lruvec {
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index aeebb9e..2809531 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4189,26 +4189,31 @@ static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
>
> #ifdef CONFIG_DEBUG_VM
> {
> - int nid, zid;
> + int nid, zid, lru;
> struct mem_cgroup_per_zone *mz;
> struct zone_reclaim_stat *rstat;
> - unsigned long recent_rotated[2] = {0, 0};
> - unsigned long recent_scanned[2] = {0, 0};
> + unsigned long recent_rotated[NR_EVICTABLE_LRU_LISTS];
>
> + memset(recent_rotated, 0, sizeof(recent_rotated));
> for_each_online_node(nid)
> for (zid = 0; zid < MAX_NR_ZONES; zid++) {
> mz = mem_cgroup_zoneinfo(memcg, nid, zid);
> rstat = &mz->lruvec.reclaim_stat;
> -
> - recent_rotated[0] += rstat->recent_rotated[0];
> - recent_rotated[1] += rstat->recent_rotated[1];
> - recent_scanned[0] += rstat->recent_scanned[0];
> - recent_scanned[1] += rstat->recent_scanned[1];
> + for_each_evictable_lru(lru)
> + recent_rotated[lru] +=
> + rstat->recent_rotated[lru];
> }
> - cb->fill(cb, "recent_rotated_anon", recent_rotated[0]);
> - cb->fill(cb, "recent_rotated_file", recent_rotated[1]);
> - cb->fill(cb, "recent_scanned_anon", recent_scanned[0]);
> - cb->fill(cb, "recent_scanned_file", recent_scanned[1]);
> +
> + cb->fill(cb, "recent_rotated_anon",
> + recent_rotated[LRU_ACTIVE_ANON]);
> + cb->fill(cb, "recent_rotated_file",
> + recent_rotated[LRU_ACTIVE_FILE]);
> + cb->fill(cb, "recent_scanned_anon",
> + recent_rotated[LRU_ACTIVE_ANON] +
> + recent_rotated[LRU_INACTIVE_ANON]);
> + cb->fill(cb, "recent_scanned_file",
> + recent_rotated[LRU_ACTIVE_FILE] +
> + recent_rotated[LRU_INACTIVE_FILE]);
> }
> #endif
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ab2d210..ea40034 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4365,10 +4365,8 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
> zone_pcp_init(zone);
> for_each_lru(lru)
> INIT_LIST_HEAD(&zone->lruvec.lists[lru]);
> - zone->lruvec.reclaim_stat.recent_rotated[0] = 0;
> - zone->lruvec.reclaim_stat.recent_rotated[1] = 0;
> - zone->lruvec.reclaim_stat.recent_scanned[0] = 0;
> - zone->lruvec.reclaim_stat.recent_scanned[1] = 0;
> + memset(&zone->lruvec.reclaim_stat, 0,
> + sizeof(struct zone_reclaim_stat));
> zap_zone_vm_stats(zone);
> zone->flags = 0;
> if (!size)
> diff --git a/mm/swap.c b/mm/swap.c
> index 9a6850b..c7bcde7 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -277,7 +277,7 @@ void rotate_reclaimable_page(struct page *page)
> }
>
> static void update_page_reclaim_stat(struct zone *zone, struct page *page,
> - int file, int rotated)
> + enum lru_list lru)
> {
> struct zone_reclaim_stat *reclaim_stat;
>
> @@ -285,9 +285,7 @@ static void update_page_reclaim_stat(struct zone *zone, struct page *page,
> if (!reclaim_stat)
> reclaim_stat = &zone->lruvec.reclaim_stat;
>
> - reclaim_stat->recent_scanned[file]++;
> - if (rotated)
> - reclaim_stat->recent_rotated[file]++;
> + reclaim_stat->recent_rotated[lru]++;
> }
>
> static void __activate_page(struct page *page, void *arg)
> @@ -295,7 +293,6 @@ static void __activate_page(struct page *page, void *arg)
> struct zone *zone = page_zone(page);
>
> if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
> - int file = page_is_file_cache(page);
> int lru = page_lru_base_type(page);
> del_page_from_lru_list(zone, page, lru);
>
> @@ -304,7 +301,7 @@ static void __activate_page(struct page *page, void *arg)
> add_page_to_lru_list(zone, page, lru);
> __count_vm_event(PGACTIVATE);
>
> - update_page_reclaim_stat(zone, page, file, 1);
> + update_page_reclaim_stat(zone, page, lru);
> }
> }
>
> @@ -482,7 +479,7 @@ static void lru_deactivate_fn(struct page *page, void *arg)
>
> if (active)
> __count_vm_event(PGDEACTIVATE);
> - update_page_reclaim_stat(zone, page, file, 0);
> + update_page_reclaim_stat(zone, page, lru);
> }
>
> /*
> @@ -646,9 +643,7 @@ EXPORT_SYMBOL(__pagevec_release);
> void lru_add_page_tail(struct zone* zone,
> struct page *page, struct page *page_tail)
> {
> - int active;
> enum lru_list lru;
> - const int file = 0;
>
> VM_BUG_ON(!PageHead(page));
> VM_BUG_ON(PageCompound(page_tail));
> @@ -660,13 +655,10 @@ void lru_add_page_tail(struct zone* zone,
> if (page_evictable(page_tail, NULL)) {
> if (PageActive(page)) {
> SetPageActive(page_tail);
> - active = 1;
> lru = LRU_ACTIVE_ANON;
> - } else {
> - active = 0;
> + } else
> lru = LRU_INACTIVE_ANON;
> - }
> - update_page_reclaim_stat(zone, page_tail, file, active);
> + update_page_reclaim_stat(zone, page_tail, lru);
> } else {
> SetPageUnevictable(page_tail);
> lru = LRU_UNEVICTABLE;
> @@ -694,17 +686,15 @@ static void __pagevec_lru_add_fn(struct page *page, void *arg)
> {
> enum lru_list lru = (enum lru_list)arg;
> struct zone *zone = page_zone(page);
> - int file = is_file_lru(lru);
> - int active = is_active_lru(lru);
>
> VM_BUG_ON(PageActive(page));
> VM_BUG_ON(PageUnevictable(page));
> VM_BUG_ON(PageLRU(page));
>
> SetPageLRU(page);
> - if (active)
> + if (is_active_lru(lru))
> SetPageActive(page);
> - update_page_reclaim_stat(zone, page, file, active);
> + update_page_reclaim_stat(zone, page, lru);
> add_page_to_lru_list(zone, page, lru);
> }
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 483b98e..fe00a22 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1355,11 +1355,7 @@ putback_inactive_pages(struct mem_cgroup_zone *mz,
> SetPageLRU(page);
> lru = page_lru(page);
> add_page_to_lru_list(zone, page, lru);
> - if (is_active_lru(lru)) {
> - int file = is_file_lru(lru);
> - int numpages = hpage_nr_pages(page);
> - reclaim_stat->recent_rotated[file] += numpages;
> - }
> + reclaim_stat->recent_rotated[lru] += hpage_nr_pages(page);
> if (put_page_testzero(page)) {
> __ClearPageLRU(page);
> __ClearPageActive(page);
> @@ -1543,8 +1539,11 @@ shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
>
> spin_lock_irq(&zone->lru_lock);
>
> - reclaim_stat->recent_scanned[0] += nr_anon;
> - reclaim_stat->recent_scanned[1] += nr_file;
> + /*
> + * Count reclaimed pages as rotated, this helps balance scan pressure
> + * between file and anonymous pages in get_scan_ratio.
> + */
> + reclaim_stat->recent_rotated[lru] += nr_reclaimed;
>
> if (current_is_kswapd())
> __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
> @@ -1685,8 +1684,6 @@ static void shrink_active_list(unsigned long nr_to_scan,
> if (global_reclaim(sc))
> zone->pages_scanned += nr_scanned;
>
> - reclaim_stat->recent_scanned[file] += nr_taken;
> -
> __count_zone_vm_events(PGREFILL, zone, nr_scanned);
> __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
> __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
> @@ -1742,7 +1739,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
> * helps balance scan pressure between file and anonymous pages in
> * get_scan_ratio.
> */
> - reclaim_stat->recent_rotated[file] += nr_rotated;
> + reclaim_stat->recent_rotated[lru] += nr_rotated;
>
> move_active_pages_to_lru(zone, &l_active, &l_hold, lru);
> move_active_pages_to_lru(zone, &l_inactive, &l_hold, lru - LRU_ACTIVE);
> @@ -1875,6 +1872,7 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
> unsigned long anon_prio, file_prio;
> unsigned long ap, fp;
> struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
> + unsigned long *recent_rotated = reclaim_stat->recent_rotated;
> u64 fraction[2], denominator;
> enum lru_list lru;
> int noswap = 0;
> @@ -1940,14 +1938,16 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
> * anon in [0], file in [1]
> */
> spin_lock_irq(&mz->zone->lru_lock);
> - if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
> - reclaim_stat->recent_scanned[0] /= 2;
> - reclaim_stat->recent_rotated[0] /= 2;
> + if (unlikely(recent_rotated[LRU_INACTIVE_ANON] +
> + recent_rotated[LRU_ACTIVE_ANON] > anon / 4)) {
> + recent_rotated[LRU_INACTIVE_ANON] /= 2;
> + recent_rotated[LRU_ACTIVE_ANON] /= 2;
> }
>
> - if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
> - reclaim_stat->recent_scanned[1] /= 2;
> - reclaim_stat->recent_rotated[1] /= 2;
> + if (unlikely(recent_rotated[LRU_INACTIVE_FILE] +
> + recent_rotated[LRU_ACTIVE_FILE] > file / 4)) {
> + recent_rotated[LRU_INACTIVE_FILE] /= 2;
> + recent_rotated[LRU_ACTIVE_FILE] /= 2;
> }
>
> /*
> @@ -1955,11 +1955,13 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
> * proportional to the fraction of recently scanned pages on
> * each list that were recently referenced and in active use.
> */
> - ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
> - ap /= reclaim_stat->recent_rotated[0] + 1;
> + ap = (anon_prio + 1) * (recent_rotated[LRU_INACTIVE_ANON] +
> + recent_rotated[LRU_ACTIVE_ANON] + 1);
> + ap /= recent_rotated[LRU_ACTIVE_ANON] + 1;
>
> - fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
> - fp /= reclaim_stat->recent_rotated[1] + 1;
> + fp = (file_prio + 1) * (recent_rotated[LRU_INACTIVE_FILE] +
> + recent_rotated[LRU_ACTIVE_FILE] + 1);
> + fp /= recent_rotated[LRU_ACTIVE_FILE] + 1;
> spin_unlock_irq(&mz->zone->lru_lock);
>
> fraction[0] = ap;
>
>
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