From: Michal Hocko <mhocko@suse.cz>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Jiri Slaby <jslaby@suse.cz>,
Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
Rik van Riel <riel@redhat.com>,
Zlatko Calusic <zcalusic@bitsync.net>,
Johannes Weiner <hannes@cmpxchg.org>,
dormando <dormando@rydia.net>,
Satoru Moriya <satoru.moriya@hds.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority
Date: Tue, 9 Apr 2013 15:27:34 +0200 [thread overview]
Message-ID: <20130409132734.GG29860@dhcp22.suse.cz> (raw)
In-Reply-To: <1365505625-9460-2-git-send-email-mgorman@suse.de>
On Tue 09-04-13 12:06:56, Mel Gorman wrote:
> The number of pages kswapd can reclaim is bound by the number of pages it
> scans which is related to the size of the zone and the scanning priority. In
> many cases the priority remains low because it's reset every SWAP_CLUSTER_MAX
> reclaimed pages but in the event kswapd scans a large number of pages it
> cannot reclaim, it will raise the priority and potentially discard a large
> percentage of the zone as sc->nr_to_reclaim is ULONG_MAX. The user-visible
> effect is a reclaim "spike" where a large percentage of memory is suddenly
> freed. It would be bad enough if this was just unused memory but because
> of how anon/file pages are balanced it is possible that applications get
> pushed to swap unnecessarily.
>
> This patch limits the number of pages kswapd will reclaim to the high
> watermark. Reclaim will still overshoot due to it not being a hard limit as
> shrink_lruvec() will ignore the sc.nr_to_reclaim at DEF_PRIORITY but it
> prevents kswapd reclaiming the world at higher priorities. The number of
> pages it reclaims is not adjusted for high-order allocations as kswapd will
> reclaim excessively if it is to balance zones for high-order allocations.
>
> Signed-off-by: Mel Gorman <mgorman@suse.de>
> Reviewed-by: Rik van Riel <riel@redhat.com>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
> ---
> mm/vmscan.c | 53 +++++++++++++++++++++++++++++------------------------
> 1 file changed, 29 insertions(+), 24 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 88c5fed..4835a7a 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2593,6 +2593,32 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
> }
>
> /*
> + * kswapd shrinks the zone by the number of pages required to reach
> + * the high watermark.
> + */
> +static void kswapd_shrink_zone(struct zone *zone,
> + struct scan_control *sc,
> + unsigned long lru_pages)
> +{
> + unsigned long nr_slab;
> + struct reclaim_state *reclaim_state = current->reclaim_state;
> + struct shrink_control shrink = {
> + .gfp_mask = sc->gfp_mask,
> + };
> +
> + /* Reclaim above the high watermark. */
> + sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone));
> + shrink_zone(zone, sc);
> +
> + reclaim_state->reclaimed_slab = 0;
> + nr_slab = shrink_slab(&shrink, sc->nr_scanned, lru_pages);
> + sc->nr_reclaimed += reclaim_state->reclaimed_slab;
> +
> + if (nr_slab == 0 && !zone_reclaimable(zone))
> + zone->all_unreclaimable = 1;
> +}
> +
> +/*
> * For kswapd, balance_pgdat() will work across all this node's zones until
> * they are all at high_wmark_pages(zone).
> *
> @@ -2619,27 +2645,16 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
> bool pgdat_is_balanced = false;
> int i;
> int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
> - unsigned long total_scanned;
> - struct reclaim_state *reclaim_state = current->reclaim_state;
> unsigned long nr_soft_reclaimed;
> unsigned long nr_soft_scanned;
> struct scan_control sc = {
> .gfp_mask = GFP_KERNEL,
> .may_unmap = 1,
> .may_swap = 1,
> - /*
> - * kswapd doesn't want to be bailed out while reclaim. because
> - * we want to put equal scanning pressure on each zone.
> - */
> - .nr_to_reclaim = ULONG_MAX,
> .order = order,
> .target_mem_cgroup = NULL,
> };
> - struct shrink_control shrink = {
> - .gfp_mask = sc.gfp_mask,
> - };
> loop_again:
> - total_scanned = 0;
> sc.priority = DEF_PRIORITY;
> sc.nr_reclaimed = 0;
> sc.may_writepage = !laptop_mode;
> @@ -2710,7 +2725,7 @@ loop_again:
> */
> for (i = 0; i <= end_zone; i++) {
> struct zone *zone = pgdat->node_zones + i;
> - int nr_slab, testorder;
> + int testorder;
> unsigned long balance_gap;
>
> if (!populated_zone(zone))
> @@ -2730,7 +2745,6 @@ loop_again:
> order, sc.gfp_mask,
> &nr_soft_scanned);
> sc.nr_reclaimed += nr_soft_reclaimed;
> - total_scanned += nr_soft_scanned;
>
> /*
> * We put equal pressure on every zone, unless
> @@ -2759,17 +2773,8 @@ loop_again:
>
> if ((buffer_heads_over_limit && is_highmem_idx(i)) ||
> !zone_balanced(zone, testorder,
> - balance_gap, end_zone)) {
> - shrink_zone(zone, &sc);
> -
> - reclaim_state->reclaimed_slab = 0;
> - nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
> - sc.nr_reclaimed += reclaim_state->reclaimed_slab;
> - total_scanned += sc.nr_scanned;
> -
> - if (nr_slab == 0 && !zone_reclaimable(zone))
> - zone->all_unreclaimable = 1;
> - }
> + balance_gap, end_zone))
> + kswapd_shrink_zone(zone, &sc, lru_pages);
>
> /*
> * If we're getting trouble reclaiming, start doing
> --
> 1.8.1.4
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2013-04-09 13:27 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-09 11:06 [PATCH 0/10] Reduce system disruption due to kswapd V2 Mel Gorman
2013-04-09 11:06 ` [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority Mel Gorman
2013-04-09 13:27 ` Michal Hocko [this message]
2013-04-10 6:47 ` Kamezawa Hiroyuki
2013-04-09 11:06 ` [PATCH 02/10] mm: vmscan: Obey proportional scanning requirements for kswapd Mel Gorman
2013-04-10 7:16 ` Kamezawa Hiroyuki
2013-04-10 14:08 ` Mel Gorman
2013-04-11 0:14 ` Kamezawa Hiroyuki
2013-04-11 9:09 ` Mel Gorman
2013-04-09 11:06 ` [PATCH 03/10] mm: vmscan: Flatten kswapd priority loop Mel Gorman
2013-04-10 7:47 ` Kamezawa Hiroyuki
2013-04-10 13:29 ` Mel Gorman
2013-04-12 2:45 ` Rik van Riel
2013-04-09 11:06 ` [PATCH 04/10] mm: vmscan: Decide whether to compact the pgdat based on reclaim progress Mel Gorman
2013-04-10 8:05 ` Kamezawa Hiroyuki
2013-04-10 13:57 ` Mel Gorman
2013-04-12 2:46 ` Rik van Riel
2013-04-09 11:07 ` [PATCH 05/10] mm: vmscan: Do not allow kswapd to scan at maximum priority Mel Gorman
2013-04-09 11:07 ` [PATCH 06/10] mm: vmscan: Have kswapd writeback pages based on dirty pages encountered, not priority Mel Gorman
2013-04-12 2:51 ` Rik van Riel
2013-04-09 11:07 ` [PATCH 07/10] mm: vmscan: Block kswapd if it is encountering pages under writeback Mel Gorman
2013-04-12 2:54 ` Rik van Riel
2013-04-09 11:07 ` [PATCH 08/10] mm: vmscan: Have kswapd shrink slab only once per priority Mel Gorman
2013-04-09 11:07 ` [PATCH 09/10] mm: vmscan: Check if kswapd should writepage once per pgdat scan Mel Gorman
2013-04-09 11:07 ` [PATCH 10/10] mm: vmscan: Move logic from balance_pgdat() to kswapd_shrink_zone() Mel Gorman
2013-04-12 2:56 ` Rik van Riel
2013-04-09 17:27 ` [PATCH 0/10] Reduce system disruption due to kswapd V2 Christoph Lameter
2013-04-10 14:14 ` Mel Gorman
2013-04-10 22:28 ` dormando
2013-04-10 23:46 ` KOSAKI Motohiro
2013-04-11 9:10 ` Mel Gorman
2013-04-11 20:13 ` Michal Hocko
2013-04-11 20:55 ` Zlatko Calusic
2013-04-12 19:40 ` Mel Gorman
2013-04-12 19:52 ` Mel Gorman
2013-04-12 20:07 ` Zlatko Calusic
2013-04-12 20:41 ` Mel Gorman
2013-04-12 21:14 ` Zlatko Calusic
2013-04-22 6:37 ` Zlatko Calusic
2013-04-22 6:43 ` Simon Jeons
2013-04-22 6:54 ` Zlatko Calusic
2013-04-22 7:12 ` Simon Jeons
-- strict thread matches above, loose matches on Subject: below --
2013-04-11 19:57 [PATCH 0/10] Reduce system disruption due to kswapd V3 Mel Gorman
2013-04-11 19:57 ` [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority Mel Gorman
2013-03-17 13:04 [RFC PATCH 0/8] Reduce system disruption due to kswapd Mel Gorman
2013-03-17 13:04 ` [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority Mel Gorman
2013-03-18 23:53 ` Simon Jeons
2013-03-19 9:55 ` Mel Gorman
2013-03-19 10:16 ` Simon Jeons
2013-03-19 10:59 ` Mel Gorman
2013-03-20 16:18 ` Michal Hocko
2013-03-21 0:52 ` Rik van Riel
2013-03-22 0:08 ` Will Huck
2013-03-21 9:47 ` Mel Gorman
2013-03-21 12:59 ` Michal Hocko
2013-03-21 0:51 ` Rik van Riel
2013-03-21 15:57 ` Johannes Weiner
2013-03-21 16:47 ` Mel Gorman
2013-03-22 0:05 ` Will Huck
2013-03-22 3:52 ` Rik van Riel
2013-03-22 3:56 ` Will Huck
2013-03-22 4:59 ` Will Huck
2013-03-22 13:01 ` Rik van Riel
2013-04-05 0:05 ` Will Huck
2013-04-07 7:32 ` Will Huck
2013-04-07 7:35 ` Will Huck
2013-04-11 5:54 ` Will Huck
2013-04-11 5:58 ` Will Huck
2013-04-12 5:46 ` Ric Mason
2013-04-12 9:34 ` Mel Gorman
2013-04-12 13:40 ` Rik van Riel
2013-03-25 9:07 ` Michal Hocko
2013-03-25 9:13 ` Jiri Slaby
2013-03-28 22:31 ` Jiri Slaby
2013-03-29 8:22 ` Michal Hocko
2013-03-30 22:07 ` Jiri Slaby
2013-04-02 11:15 ` Mel Gorman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130409132734.GG29860@dhcp22.suse.cz \
--to=mhocko@suse.cz \
--cc=Valdis.Kletnieks@vt.edu \
--cc=akpm@linux-foundation.org \
--cc=dormando@rydia.net \
--cc=hannes@cmpxchg.org \
--cc=jslaby@suse.cz \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=riel@redhat.com \
--cc=satoru.moriya@hds.com \
--cc=zcalusic@bitsync.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).