From: Michal Hocko <mhocko@kernel.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Jia He <hejianet@gmail.com>, Mel Gorman <mgorman@suse.de>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com
Subject: Re: [PATCH 9/9] mm: remove unnecessary back-off function when retrying page reclaim
Date: Wed, 1 Mar 2017 15:56:56 +0100 [thread overview]
Message-ID: <20170301145656.GA11730@dhcp22.suse.cz> (raw)
In-Reply-To: <20170228214007.5621-10-hannes@cmpxchg.org>
On Tue 28-02-17 16:40:07, Johannes Weiner wrote:
> The backoff mechanism is not needed. If we have MAX_RECLAIM_RETRIES
> loops without progress, we'll OOM anyway; backing off might cut one or
> two iterations off that in the rare OOM case. If we have intermittent
> success reclaiming a few pages, the backoff function gets reset also,
> and so is of little help in these scenarios.
Yes, as already mentioned elsewhere the original intention was to a more
graceful oom convergence when we are trashing over last few reclaimable
pages but as the code evolved the result is not all that great.
> We might want a backoff function for when there IS progress, but not
> enough to be satisfactory. But this isn't that. Remove it.
Completely agreed.
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/page_alloc.c | 15 ++++++---------
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9ac639864bed..223644afed28 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3511,11 +3511,10 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
> /*
> * Checks whether it makes sense to retry the reclaim to make a forward progress
> * for the given allocation request.
> - * The reclaim feedback represented by did_some_progress (any progress during
> - * the last reclaim round) and no_progress_loops (number of reclaim rounds without
> - * any progress in a row) is considered as well as the reclaimable pages on the
> - * applicable zone list (with a backoff mechanism which is a function of
> - * no_progress_loops).
> + *
> + * We give up when we either have tried MAX_RECLAIM_RETRIES in a row
> + * without success, or when we couldn't even meet the watermark if we
> + * reclaimed all remaining pages on the LRU lists.
> *
> * Returns true if a retry is viable or false to enter the oom path.
> */
> @@ -3560,13 +3559,11 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
> bool wmark;
>
> available = reclaimable = zone_reclaimable_pages(zone);
> - available -= DIV_ROUND_UP((*no_progress_loops) * available,
> - MAX_RECLAIM_RETRIES);
> available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
>
> /*
> - * Would the allocation succeed if we reclaimed the whole
> - * available?
> + * Would the allocation succeed if we reclaimed all
> + * reclaimable pages?
> */
> wmark = __zone_watermark_ok(zone, order, min_wmark,
> ac_classzone_idx(ac), alloc_flags, available);
> --
> 2.11.1
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-03-01 15:43 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-28 21:39 [PATCH 0/9] mm: kswapd spinning on unreclaimable nodes - fixes and cleanups Johannes Weiner
2017-02-28 21:39 ` [PATCH 1/9] mm: fix 100% CPU kswapd busyloop on unreclaimable nodes Johannes Weiner
2017-03-02 3:23 ` Hillf Danton
2017-03-02 23:30 ` Shakeel Butt
2017-03-03 1:26 ` Minchan Kim
2017-03-03 7:59 ` Michal Hocko
2017-03-06 1:37 ` Minchan Kim
2017-03-06 16:24 ` Johannes Weiner
2017-03-07 0:59 ` Hillf Danton
2017-03-07 7:28 ` Minchan Kim
2017-03-07 10:17 ` Michal Hocko
2017-03-07 16:56 ` Johannes Weiner
2017-03-09 14:20 ` Mel Gorman
2017-02-28 21:40 ` [PATCH 2/9] mm: fix check for reclaimable pages in PF_MEMALLOC reclaim throttling Johannes Weiner
2017-03-01 15:02 ` Michal Hocko
2017-03-02 3:25 ` Hillf Danton
2017-02-28 21:40 ` [PATCH 3/9] mm: remove seemingly spurious reclaimability check from laptop_mode gating Johannes Weiner
2017-03-01 15:06 ` Michal Hocko
2017-03-01 15:17 ` Mel Gorman
2017-03-02 3:27 ` Hillf Danton
2017-02-28 21:40 ` [PATCH 4/9] mm: remove unnecessary reclaimability check from NUMA balancing target Johannes Weiner
2017-03-01 15:14 ` Michal Hocko
2017-03-02 3:28 ` Hillf Danton
2017-02-28 21:40 ` [PATCH 5/9] mm: don't avoid high-priority reclaim on unreclaimable nodes Johannes Weiner
2017-03-01 15:21 ` Michal Hocko
2017-03-02 3:31 ` Hillf Danton
2017-02-28 21:40 ` [PATCH 6/9] mm: don't avoid high-priority reclaim on memcg limit reclaim Johannes Weiner
2017-03-01 15:40 ` Michal Hocko
2017-03-01 17:36 ` Johannes Weiner
2017-03-01 19:13 ` Michal Hocko
2017-03-02 3:32 ` Hillf Danton
2017-02-28 21:40 ` [PATCH 7/9] mm: delete NR_PAGES_SCANNED and pgdat_reclaimable() Johannes Weiner
2017-03-01 15:41 ` Michal Hocko
2017-03-02 3:34 ` Hillf Danton
2017-02-28 21:40 ` [PATCH 8/9] Revert "mm, vmscan: account for skipped pages as a partial scan" Johannes Weiner
2017-03-01 15:51 ` Michal Hocko
2017-03-02 3:36 ` Hillf Danton
2017-02-28 21:40 ` [PATCH 9/9] mm: remove unnecessary back-off function when retrying page reclaim Johannes Weiner
2017-03-01 14:56 ` Michal Hocko [this message]
2017-03-02 3:37 ` Hillf Danton
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=20170301145656.GA11730@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=hejianet@gmail.com \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
/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).