From: Mel Gorman <mgorman@techsingularity.net>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
NeilBrown <neilb@suse.de>, Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Matthew Wilcox <willy@infradead.org>,
Michal Hocko <mhocko@suse.com>,
Dave Chinner <david@fromorbit.com>,
Rik van Riel <riel@surriel.com>, Vlastimil Babka <vbabka@suse.cz>,
Johannes Weiner <hannes@cmpxchg.org>,
Jonathan Corbet <corbet@lwn.net>, Linux-MM <linux-mm@kvack.org>,
Linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/8] mm/vmscan: Throttle reclaim when no progress is being made
Date: Wed, 24 Nov 2021 14:35:59 +0000 [thread overview]
Message-ID: <20211124143559.GI3366@techsingularity.net> (raw)
In-Reply-To: <20211124014914.GB265983@magnolia>
On Tue, Nov 23, 2021 at 05:49:14PM -0800, Darrick J. Wong wrote:
> > Ever since Christoph broke swapfiles, I've been carrying around a little
> > fstest in my dev tree[1] that tries to exercise paging things in and out
> > of a swapfile. Sadly I've been trapped in about three dozen customer
> > escalations for over a month, which means I haven't been able to do much
> > upstream in weeks. Like submit this test upstream. :(
> >
> > Now that I've finally gotten around to trying out a 5.16-rc2 build, I
> > notice that the runtime of this test has gone from ~5s to 2 hours.
> > Among other things that it does, the test sets up a cgroup with a memory
> > controller limiting the memory usage to 25MB, then runs a program that
> > tries to dirty 50MB of memory. There's 2GB of memory in the VM, so
> > we're not running reclaim globally, but the cgroup gets throttled very
> > severely.
> >
> > AFAICT the system is mostly idle, but it's difficult to tell because ps
> > and top also get stuck waiting for this cgroup for whatever reason. My
> > uninformed spculation is that usemem_and_swapoff takes a page fault
> > while dirtying the 50MB memory buffer, prepares to pull a page in from
> > swap, tries to evict another page to stay under the memcg limit, but
> > that decides that it's making no progress and calls
> > reclaim_throttle(..., VMSCAN_THROTTLE_NOPROGRESS).
> >
> > The sleep is uninterruptible, so I can't even kill -9 fstests to shut it
> > down. Eventually we either finish the test or (for the mlock part) the
> > OOM killer actually kills the process, but this takes a very long time.
> >
> > Any thoughts? For now I can just hack around this by skipping
> > reclaim_throttle if cgroup_reclaim() == true, but that's probably not
> > the correct fix. :)
>
> Update: after adding timing information to usemem_and_swapoff, it looks
> like dirtying the 50MB buffer takes ~22s (up from 0.06s on 5.15). The
> mlock call stalls for ~280s until the OOM killer kills it (up from
> nearly instantaneous on 5.15), and the swapon/swapoff variant takes
> 20 minutes to hours depending on the run.
>
Can you try the patch below please? I think I'm running the test
correctly and it finishes for me in 16 seconds with this applied
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 07db03883062..d9166e94eb95 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1057,7 +1057,17 @@ void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
break;
case VMSCAN_THROTTLE_NOPROGRESS:
- timeout = HZ/2;
+ timeout = 1;
+
+ /*
+ * If kswapd is disabled, reschedule if necessary but do not
+ * throttle as the system is likely near OOM.
+ */
+ if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES) {
+ cond_resched();
+ return;
+ }
+
break;
case VMSCAN_THROTTLE_ISOLATED:
timeout = HZ/50;
@@ -3395,7 +3405,7 @@ static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
return;
/* Throttle if making no progress at high prioities. */
- if (sc->priority < DEF_PRIORITY - 2)
+ if (sc->priority < DEF_PRIORITY - 2 && !sc->nr_reclaimed)
reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS);
}
@@ -3415,6 +3425,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
unsigned long nr_soft_scanned;
gfp_t orig_mask;
pg_data_t *last_pgdat = NULL;
+ pg_data_t *first_pgdat = NULL;
/*
* If the number of buffer_heads in the machine exceeds the maximum
@@ -3478,14 +3489,18 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
/* need some check for avoid more shrink_zone() */
}
+ if (!first_pgdat)
+ first_pgdat = zone->zone_pgdat;
+
/* See comment about same check for global reclaim above */
if (zone->zone_pgdat == last_pgdat)
continue;
last_pgdat = zone->zone_pgdat;
shrink_node(zone->zone_pgdat, sc);
- consider_reclaim_throttle(zone->zone_pgdat, sc);
}
+ consider_reclaim_throttle(first_pgdat, sc);
+
/*
* Restore to original mask to avoid the impact on the caller if we
* promoted it to __GFP_HIGHMEM.
next prev parent reply other threads:[~2021-11-24 14:36 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-22 14:46 [PATCH v5 0/8] Remove dependency on congestion_wait in mm/ Mel Gorman
2021-10-22 14:46 ` [PATCH 1/8] mm/vmscan: Throttle reclaim until some writeback completes if congested Mel Gorman
2021-10-22 14:46 ` [PATCH 2/8] mm/vmscan: Throttle reclaim and compaction when too may pages are isolated Mel Gorman
2021-10-22 14:46 ` [PATCH 3/8] mm/vmscan: Throttle reclaim when no progress is being made Mel Gorman
2021-11-24 1:19 ` Darrick J. Wong
2021-11-24 1:49 ` Darrick J. Wong
2021-11-24 14:35 ` Mel Gorman [this message]
2021-11-24 18:02 ` Darrick J. Wong
2021-11-24 10:32 ` Mel Gorman
2021-11-24 10:43 ` Vlastimil Babka
2021-11-24 10:53 ` Mel Gorman
2021-11-24 17:24 ` Mike Galbraith
2021-10-22 14:46 ` [PATCH 4/8] mm/writeback: Throttle based on page writeback instead of congestion Mel Gorman
2021-10-22 14:46 ` [PATCH 5/8] mm/page_alloc: Remove the throttling logic from the page allocator Mel Gorman
2021-10-25 10:07 ` Vlastimil Babka
2021-10-22 14:46 ` [PATCH 6/8] mm/vmscan: Centralise timeout values for reclaim_throttle Mel Gorman
2021-10-22 14:46 ` [PATCH 7/8] mm/vmscan: Increase the timeout if page reclaim is not making progress Mel Gorman
2021-10-22 14:46 ` [PATCH 8/8] mm/vmscan: Delay waking of tasks throttled on NOPROGRESS Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2021-10-19 9:01 [PATCH v4 0/8] Remove dependency on congestion_wait in mm/ Mel Gorman
2021-10-19 9:01 ` [PATCH 3/8] mm/vmscan: Throttle reclaim when no progress is being made Mel Gorman
2021-10-08 13:53 [PATCH v3 0/8] Remove dependency on congestion_wait in mm/ Mel Gorman
2021-10-08 13:53 ` [PATCH 3/8] mm/vmscan: Throttle reclaim when no progress is being made Mel Gorman
2021-10-14 12:31 ` Vlastimil Babka
2021-10-14 13:03 ` Mel Gorman
2021-10-14 15:45 ` Vlastimil Babka
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