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Date: Wed, 13 Jan 2010 19:31:52 +0900
From: Minchan Kim <minchan.kim@...il.com>
To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 2/3][v2] vmstat: add anon_scan_ratio field to zoneinfo
Hi, Kosaki.
On Wed, Jan 13, 2010 at 5:21 PM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
> Changelog
> from v1
> - get_anon_scan_ratio don't tak zone->lru_lock anymore
> because zoneinfo_show_print takes zone->lock.
When I saw this changelog first, I got confused.
That's because there is no relation between lru_lock and lock in zone.
You mean zoneinfo is allowed to have a stale data?
Tend to agree with it.
>
>
> ======================================
> Vmscan folks was asked "why does my system makes so much swap-out?"
> in lkml at several times.
> At that time, I made the debug patch to show recent_anon_{scanned/rorated}
> parameter at least three times.
>
> Thus, its parameter should be showed on /proc/zoneinfo. It help
> vmscan folks debugging.
I support this suggestion.
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Reviewed-by: Rik van Riel <riel@...hat.com>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> ---
> include/linux/swap.h | 2 ++
> mm/vmscan.c | 50 ++++++++++++++++++++++++++++++++++++--------------
> mm/vmstat.c | 7 +++++--
> 3 files changed, 43 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index a2602a8..e95d7ed 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -280,6 +280,8 @@ extern void scan_unevictable_unregister_node(struct node *node);
> extern int kswapd_run(int nid);
> extern void kswapd_stop(int nid);
>
> +unsigned long get_anon_scan_ratio(struct zone *zone, struct mem_cgroup *memcg, int swappiness);
Today Andrew said to me. :)
"The vmscan.c code makes an effort to look nice in an 80-col display."
> +
> #ifdef CONFIG_MMU
> /* linux/mm/shmem.c */
> extern int shmem_unuse(swp_entry_t entry, struct page *page);
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 640486b..0900931 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1493,8 +1493,8 @@ static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
> * percent[0] specifies how much pressure to put on ram/swap backed
> * memory, while percent[1] determines pressure on the file LRUs.
> */
> -static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
> - unsigned long *percent)
> +static void __get_scan_ratio(struct zone *zone, struct scan_control *sc,
> + int need_update, unsigned long *percent)
> {
> unsigned long anon, file, free;
> unsigned long anon_prio, file_prio;
> @@ -1535,18 +1535,19 @@ static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
> *
> * anon in [0], file in [1]
> */
> - if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
> - spin_lock_irq(&zone->lru_lock);
> - reclaim_stat->recent_scanned[0] /= 2;
> - reclaim_stat->recent_rotated[0] /= 2;
> - spin_unlock_irq(&zone->lru_lock);
> - }
> -
> - if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
> - spin_lock_irq(&zone->lru_lock);
> - reclaim_stat->recent_scanned[1] /= 2;
> - reclaim_stat->recent_rotated[1] /= 2;
> - spin_unlock_irq(&zone->lru_lock);
Why do you add new parameter 'need_update'?
Do you see any lru_lock heavy contention? (reclaim VS cat /proc/zoneinfo)
I think maybe not.
I am not sure no locking version is needed.
> + if (need_update) {
> + if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
> + spin_lock_irq(&zone->lru_lock);
> + reclaim_stat->recent_scanned[0] /= 2;
> + reclaim_stat->recent_rotated[0] /= 2;
> + spin_unlock_irq(&zone->lru_lock);
> + }
> + if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
> + spin_lock_irq(&zone->lru_lock);
> + reclaim_stat->recent_scanned[1] /= 2;
> + reclaim_stat->recent_rotated[1] /= 2;
> + spin_unlock_irq(&zone->lru_lock);
> + }
> }
>
> /*
> @@ -1572,6 +1573,27 @@ static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
> percent[1] = 100 - percent[0];
> }
>
> +static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
> + unsigned long *percent)
> +{
> + __get_scan_ratio(zone, sc, 1, percent);
> +}
> +
If we really need this version and your changelog is right,
Let's add 'note'. ;-)
/* Caller have to hold zone->lock */
> +unsigned long get_anon_scan_ratio(struct zone *zone, struct mem_cgroup *memcg, int swappiness)
> +{
> + unsigned long percent[2];
> + struct scan_control sc = {
> + .may_swap = 1,
> + .swappiness = swappiness,
> + .mem_cgroup = memcg,
> + };
> +
> + __get_scan_ratio(zone, &sc, 0, percent);
> +
> + return percent[0];
> +}
> +
> +
> /*
> * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
> * until we collected @swap_cluster_max pages to scan.
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 6051fba..f690117 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -15,6 +15,7 @@
> #include <linux/cpu.h>
> #include <linux/vmstat.h>
> #include <linux/sched.h>
> +#include <linux/swap.h>
>
> #ifdef CONFIG_VM_EVENT_COUNTERS
> DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
> @@ -760,11 +761,13 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
> "\n all_unreclaimable: %u"
> "\n prev_priority: %i"
> "\n start_pfn: %lu"
> - "\n inactive_ratio: %u",
> + "\n inactive_ratio: %u"
> + "\n anon_scan_ratio: %lu",
> zone_is_all_unreclaimable(zone),
> zone->prev_priority,
> zone->zone_start_pfn,
> - zone->inactive_ratio);
> + zone->inactive_ratio,
> + get_anon_scan_ratio(zone, NULL, vm_swappiness));
> seq_putc(m, '\n');
> }
>
> --
> 1.6.5.2
>
>
>
>
--
Kind regards,
Minchan Kim
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