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Date: Tue, 10 Feb 2009 19:57:01 +0900
From: MinChan Kim <minchan.kim@...il.com>
To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
LKML <linux-kernel@...r.kernel.org>,
linux-mm <linux-mm@...ck.org>, Rik van Riel <riel@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm: remove zone->prev_prioriy
Hi, Kosaki-san.
As you know, prev_priority is used as a measure of how much stress page reclaim.
But now we doesn't need it due to split-lru's way.
I think it would be better to remain why prev_priority isn't needed any more
and how split-lru can replace prev_priority's role in changelog.
In future, it help mm newbies understand change history, I think.
On Tue, Feb 10, 2009 at 6:42 PM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
>
> KAMEZAWA Hiroyuki sugessted to remove zone->prev_priority.
> it's because Split-LRU VM doesn't use this parameter at all.
>
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> ---
> include/linux/memcontrol.h | 27 -------------------------
> include/linux/mmzone.h | 15 --------------
> mm/memcontrol.c | 31 -----------------------------
> mm/page_alloc.c | 2 -
> mm/vmscan.c | 48 ++-------------------------------------------
> mm/vmstat.c | 2 -
> 6 files changed, 3 insertions(+), 122 deletions(-)
>
> Index: b/mm/memcontrol.c
> ===================================================================
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -150,8 +150,6 @@ struct mem_cgroup {
> */
> spinlock_t reclaim_param_lock;
>
> - int prev_priority; /* for recording reclaim priority */
> -
> /*
> * While reclaiming in a hiearchy, we cache the last child we
> * reclaimed from. Protected by hierarchy_mutex
> @@ -464,35 +462,6 @@ int mem_cgroup_calc_mapped_ratio(struct
> return (int)((rss * 100L) / total);
> }
>
> -/*
> - * prev_priority control...this will be used in memory reclaim path.
> - */
> -int mem_cgroup_get_reclaim_priority(struct mem_cgroup *mem)
> -{
> - int prev_priority;
> -
> - spin_lock(&mem->reclaim_param_lock);
> - prev_priority = mem->prev_priority;
> - spin_unlock(&mem->reclaim_param_lock);
> -
> - return prev_priority;
> -}
> -
> -void mem_cgroup_note_reclaim_priority(struct mem_cgroup *mem, int priority)
> -{
> - spin_lock(&mem->reclaim_param_lock);
> - if (priority < mem->prev_priority)
> - mem->prev_priority = priority;
> - spin_unlock(&mem->reclaim_param_lock);
> -}
> -
> -void mem_cgroup_record_reclaim_priority(struct mem_cgroup *mem, int priority)
> -{
> - spin_lock(&mem->reclaim_param_lock);
> - mem->prev_priority = priority;
> - spin_unlock(&mem->reclaim_param_lock);
> -}
> -
> static int calc_inactive_ratio(struct mem_cgroup *memcg, unsigned long *present_pages)
> {
> unsigned long active;
> Index: b/mm/vmscan.c
> ===================================================================
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1174,20 +1174,6 @@ done:
> }
>
> /*
> - * We are about to scan this zone at a certain priority level. If that priority
> - * level is smaller (ie: more urgent) than the previous priority, then note
> - * that priority level within the zone. This is done so that when the next
> - * process comes in to scan this zone, it will immediately start out at this
> - * priority level rather than having to build up its own scanning priority.
> - * Here, this priority affects only the reclaim-mapped threshold.
> - */
> -static inline void note_zone_scanning_priority(struct zone *zone, int priority)
> -{
> - if (priority < zone->prev_priority)
> - zone->prev_priority = priority;
> -}
> -
> -/*
> * This moves pages from the active list to the inactive list.
> *
> * We move them the other way if the page is referenced by one or more
> @@ -1553,22 +1539,18 @@ static void shrink_zones(int priority, s
> if (scanning_global_lru(sc)) {
> if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
> continue;
> - note_zone_scanning_priority(zone, priority);
>
> if (zone_is_all_unreclaimable(zone) &&
> priority != DEF_PRIORITY)
> continue; /* Let kswapd poll it */
> - sc->all_unreclaimable = 0;
> +
> } else {
> /*
> * Ignore cpuset limitation here. We just want to reduce
> * # of used pages by us regardless of memory shortage.
> */
> - sc->all_unreclaimable = 0;
> - mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
> - priority);
> }
> -
> + sc->all_unreclaimable = 0;
> shrink_zone(priority, zone, sc);
> }
> }
> @@ -1676,11 +1658,8 @@ out:
>
> if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
> continue;
> -
> - zone->prev_priority = priority;
> }
> - } else
> - mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
> + }
>
> delayacct_freepages_end();
>
> @@ -1769,11 +1748,6 @@ static unsigned long balance_pgdat(pg_da
> .mem_cgroup = NULL,
> .isolate_pages = isolate_pages_global,
> };
> - /*
> - * temp_priority is used to remember the scanning priority at which
> - * this zone was successfully refilled to free_pages == pages_high.
> - */
> - int temp_priority[MAX_NR_ZONES];
>
> loop_again:
> total_scanned = 0;
> @@ -1781,9 +1755,6 @@ loop_again:
> sc.may_writepage = !laptop_mode;
> count_vm_event(PAGEOUTRUN);
>
> - for (i = 0; i < pgdat->nr_zones; i++)
> - temp_priority[i] = DEF_PRIORITY;
> -
> for (priority = DEF_PRIORITY; priority >= 0; priority--) {
> int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
> unsigned long lru_pages = 0;
> @@ -1854,9 +1825,7 @@ loop_again:
> if (!zone_watermark_ok(zone, order, zone->pages_high,
> end_zone, 0))
> all_zones_ok = 0;
> - temp_priority[i] = priority;
> sc.nr_scanned = 0;
> - note_zone_scanning_priority(zone, priority);
> /*
> * We put equal pressure on every zone, unless one
> * zone has way too many pages free already.
> @@ -1903,16 +1872,6 @@ loop_again:
> break;
> }
> out:
> - /*
> - * Note within each zone the priority level at which this zone was
> - * brought into a happy state. So that the next thread which scans this
> - * zone will start out at that priority level.
> - */
> - for (i = 0; i < pgdat->nr_zones; i++) {
> - struct zone *zone = pgdat->node_zones + i;
> -
> - zone->prev_priority = temp_priority[i];
> - }
> if (!all_zones_ok) {
> cond_resched();
>
> @@ -2321,7 +2280,6 @@ static int __zone_reclaim(struct zone *z
> */
> priority = ZONE_RECLAIM_PRIORITY;
> do {
> - note_zone_scanning_priority(zone, priority);
> shrink_zone(priority, zone, &sc);
> priority--;
> } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
> Index: b/include/linux/mmzone.h
> ===================================================================
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -337,21 +337,6 @@ struct zone {
> atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
>
> /*
> - * prev_priority holds the scanning priority for this zone. It is
> - * defined as the scanning priority at which we achieved our reclaim
> - * target at the previous try_to_free_pages() or balance_pgdat()
> - * invokation.
> - *
> - * We use prev_priority as a measure of how much stress page reclaim is
> - * under - it drives the swappiness decision: whether to unmap mapped
> - * pages.
> - *
> - * Access to both this field is quite racy even on uniprocessor. But
> - * it is expected to average out OK.
> - */
> - int prev_priority;
> -
> - /*
> * The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
> * this zone's LRU. Maintained by the pageout code.
> */
> Index: b/mm/page_alloc.c
> ===================================================================
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3516,8 +3516,6 @@ static void __paginginit free_area_init_
> zone_seqlock_init(zone);
> zone->zone_pgdat = pgdat;
>
> - zone->prev_priority = DEF_PRIORITY;
> -
> zone_pcp_init(zone);
> for_each_lru(l) {
> INIT_LIST_HEAD(&zone->lru[l].list);
> Index: b/mm/vmstat.c
> ===================================================================
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -775,11 +775,9 @@ static void zoneinfo_show_print(struct s
> }
> seq_printf(m,
> "\n all_unreclaimable: %u"
> - "\n prev_priority: %i"
> "\n start_pfn: %lu"
> "\n inactive_ratio: %u",
> zone_is_all_unreclaimable(zone),
> - zone->prev_priority,
> zone->zone_start_pfn,
> zone->inactive_ratio);
> seq_putc(m, '\n');
> Index: b/include/linux/memcontrol.h
> ===================================================================
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -88,14 +88,7 @@ extern void mem_cgroup_end_migration(str
> /*
> * For memory reclaim.
> */
> -extern int mem_cgroup_calc_mapped_ratio(struct mem_cgroup *mem);
> extern long mem_cgroup_reclaim_imbalance(struct mem_cgroup *mem);
> -
> -extern int mem_cgroup_get_reclaim_priority(struct mem_cgroup *mem);
> -extern void mem_cgroup_note_reclaim_priority(struct mem_cgroup *mem,
> - int priority);
> -extern void mem_cgroup_record_reclaim_priority(struct mem_cgroup *mem,
> - int priority);
> int mem_cgroup_inactive_anon_is_low(struct mem_cgroup *memcg);
> unsigned long mem_cgroup_zone_nr_pages(struct mem_cgroup *memcg,
> struct zone *zone,
> @@ -209,31 +202,11 @@ static inline void mem_cgroup_end_migrat
> {
> }
>
> -static inline int mem_cgroup_calc_mapped_ratio(struct mem_cgroup *mem)
> -{
> - return 0;
> -}
> -
> static inline int mem_cgroup_reclaim_imbalance(struct mem_cgroup *mem)
> {
> return 0;
> }
>
> -static inline int mem_cgroup_get_reclaim_priority(struct mem_cgroup *mem)
> -{
> - return 0;
> -}
> -
> -static inline void mem_cgroup_note_reclaim_priority(struct mem_cgroup *mem,
> - int priority)
> -{
> -}
> -
> -static inline void mem_cgroup_record_reclaim_priority(struct mem_cgroup *mem,
> - int priority)
> -{
> -}
> -
> static inline bool mem_cgroup_disabled(void)
> {
> return true;
>
>
>
> --
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>
--
Kinds regards,
MinChan Kim
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