From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Minchan Kim <minchan@kernel.org>, Michal Hocko <mhocko@suse.cz>,
Vlastimil Babka <vbabka@suse.cz>, Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 5/5] mm, vmscan: Account for skipped pages as a partial scan
Date: Tue, 26 Jul 2016 17:16:22 +0900 [thread overview]
Message-ID: <20160726081621.GC15721@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <1469110261-7365-6-git-send-email-mgorman@techsingularity.net>
On Thu, Jul 21, 2016 at 03:11:01PM +0100, Mel Gorman wrote:
> Page reclaim determines whether a pgdat is unreclaimable by examining how
> many pages have been scanned since a page was freed and comparing that to
> the LRU sizes. Skipped pages are not reclaim candidates but contribute to
> scanned. This can prematurely mark a pgdat as unreclaimable and trigger
> an OOM kill.
>
> This patch accounts for skipped pages as a partial scan so that an
> unreclaimable pgdat will still be marked as such but by scaling the cost
> of a skip, it'll avoid the pgdat being marked prematurely.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> ---
> mm/vmscan.c | 20 ++++++++++++++++++--
> 1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 6810d81f60c7..e5af357dd4ac 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1424,7 +1424,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> LIST_HEAD(pages_skipped);
>
> for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan &&
> - !list_empty(src); scan++) {
> + !list_empty(src);) {
> struct page *page;
>
> page = lru_to_page(src);
> @@ -1438,6 +1438,12 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> continue;
> }
>
> + /*
> + * Account for scanned and skipped separetly to avoid the pgdat
> + * being prematurely marked unreclaimable by pgdat_reclaimable.
> + */
> + scan++;
> +
This logic has potential unbounded retry problem. src would not become
empty if __isolate_lru_page() return -EBUSY since we move failed page
to src list again in this case.
Thanks.
> switch (__isolate_lru_page(page, mode)) {
> case 0:
> nr_pages = hpage_nr_pages(page);
> @@ -1465,14 +1471,24 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> */
> if (!list_empty(&pages_skipped)) {
> int zid;
> + unsigned long total_skipped = 0;
>
> - list_splice(&pages_skipped, src);
> for (zid = 0; zid < MAX_NR_ZONES; zid++) {
> if (!nr_skipped[zid])
> continue;
>
> __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
> + total_skipped += nr_skipped[zid];
> }
> +
> + /*
> + * Account skipped pages as a partial scan as the pgdat may be
> + * close to unreclaimable. If the LRU list is empty, account
> + * skipped pages as a full scan.
> + */
> + scan += list_empty(src) ? total_skipped : total_skipped >> 2;
> +
> + list_splice(&pages_skipped, src);
> }
> *nr_scanned = scan;
> trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, scan,
> --
> 2.6.4
>
> --
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next prev parent reply other threads:[~2016-07-26 8:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-21 14:10 [PATCH 0/5] Candidate fixes for premature OOM kills with node-lru v2 Mel Gorman
2016-07-21 14:10 ` [PATCH 1/5] mm: add per-zone lru list stat Mel Gorman
2016-07-22 15:51 ` Johannes Weiner
2016-07-21 14:10 ` [PATCH 2/5] mm, vmscan: Remove highmem_file_pages Mel Gorman
2016-07-22 15:53 ` Johannes Weiner
2016-07-25 8:09 ` Minchan Kim
2016-07-25 9:23 ` [PATCH] mm, vmscan: remove highmem_file_pages -fix Mel Gorman
2016-07-21 14:10 ` [PATCH 3/5] mm: Remove reclaim and compaction retry approximations Mel Gorman
2016-07-22 15:57 ` Johannes Weiner
2016-07-25 8:18 ` Minchan Kim
2016-07-21 14:11 ` [PATCH 4/5] mm: consider per-zone inactive ratio to deactivate Mel Gorman
2016-07-21 15:52 ` Johannes Weiner
2016-07-21 14:11 ` [PATCH 5/5] mm, vmscan: Account for skipped pages as a partial scan Mel Gorman
2016-07-22 16:02 ` Johannes Weiner
2016-07-25 8:39 ` Minchan Kim
2016-07-25 9:52 ` Mel Gorman
2016-07-26 8:16 ` Joonsoo Kim [this message]
2016-07-26 8:26 ` Joonsoo Kim
2016-07-26 8:11 ` [PATCH 0/5] Candidate fixes for premature OOM kills with node-lru v2 Joonsoo Kim
2016-07-26 12:50 ` Mel Gorman
2016-07-28 6:44 ` Joonsoo Kim
2016-07-28 10:27 ` Mel Gorman
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