From: Mel Gorman <mgorman@techsingularity.net>
To: dsterba@suse.cz, Matthew Wilcox <willy@infradead.org>,
Linux-MM <linux-mm@kvack.org>, NeilBrown <neilb@suse.de>,
Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
"Darrick J . Wong" <djwong@kernel.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-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 0/5] Remove dependency on congestion_wait in mm/
Date: Tue, 21 Sep 2021 12:18:17 +0100 [thread overview]
Message-ID: <20210921111816.GS3959@techsingularity.net> (raw)
In-Reply-To: <20210920141152.GM9286@twin.jikos.cz>
On Mon, Sep 20, 2021 at 04:11:52PM +0200, David Sterba wrote:
> On Mon, Sep 20, 2021 at 01:50:58PM +0100, Mel Gorman wrote:
> > On Mon, Sep 20, 2021 at 12:42:44PM +0100, Matthew Wilcox wrote:
> > > On Mon, Sep 20, 2021 at 09:54:31AM +0100, Mel Gorman wrote:
> > > > This has been lightly tested only and the testing was useless as the
> > > > relevant code was not executed. The workload configurations I had that
> > > > used to trigger these corner cases no longer work (yey?) and I'll need
> > > > to implement a new synthetic workload. If someone is aware of a realistic
> > > > workload that forces reclaim activity to the point where reclaim stalls
> > > > then kindly share the details.
> > >
> > > The stereeotypical "stalling on I/O" problem is to plug in one of the
> > > crap USB drives you were given at a trade show and simply
> > > dd if=/dev/zero of=/dev/sdb
> > > sync
> > >
> >
> > The test machines are 1500KM away so plugging in a USB stick but worst
> > comes to the worst, I could test it on a laptop.
>
> There's a device mapper target dm-delay [1] that as it says delays the
> reads and writes, so you could try to emulate the slow USB that way.
>
> [1] https://www.kernel.org/doc/html/latest/admin-guide/device-mapper/delay.html
Ah, thanks for that tip. I wondered if something like this existed and
clearly did not search hard enough. I was able to reproduce the problem
without throttling but this could still be useful if examining cases
where there are 2 or more BDIs with variable speeds.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2021-09-21 11:18 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-20 8:54 [RFC PATCH 0/5] Remove dependency on congestion_wait in mm/ Mel Gorman
2021-09-20 8:54 ` [PATCH 1/5] mm/vmscan: Throttle reclaim until some writeback completes if congested Mel Gorman
2021-09-20 23:19 ` NeilBrown
2021-09-21 11:12 ` Mel Gorman
2021-09-21 21:27 ` NeilBrown
2021-09-21 0:13 ` NeilBrown
2021-09-21 10:58 ` Mel Gorman
2021-09-21 21:40 ` NeilBrown
2021-09-22 6:04 ` Dave Chinner
2021-09-22 8:03 ` Mel Gorman
2021-09-20 8:54 ` [PATCH 2/5] mm/vmscan: Throttle reclaim and compaction when too may pages are isolated Mel Gorman
2021-09-20 23:27 ` NeilBrown
2021-09-21 11:03 ` Mel Gorman
2021-09-21 18:45 ` Yang Shi
2021-09-22 8:11 ` Mel Gorman
2021-09-20 8:54 ` [PATCH 3/5] mm/vmscan: Throttle reclaim when no progress is being made Mel Gorman
2021-09-20 23:31 ` NeilBrown
2021-09-21 11:16 ` Mel Gorman
2021-09-21 21:46 ` NeilBrown
2021-09-22 9:21 ` Mel Gorman
2021-09-20 8:54 ` [PATCH 4/5] mm/writeback: Throttle based on page writeback instead of congestion Mel Gorman
2021-09-20 8:54 ` [PATCH 5/5] mm/page_alloc: Remove the throttling logic from the page allocator Mel Gorman
2021-09-20 11:42 ` [RFC PATCH 0/5] Remove dependency on congestion_wait in mm/ Matthew Wilcox
2021-09-20 12:50 ` Mel Gorman
2021-09-20 14:11 ` David Sterba
2021-09-21 11:18 ` Mel Gorman [this message]
2021-09-20 19:51 ` Mel Gorman
2021-09-21 20:46 ` Dave Chinner
2021-09-22 17:52 ` Mel Gorman
[not found] ` <20210922121620.4716-1-hdanton@sina.com>
2021-09-22 14:13 ` [PATCH 1/5] mm/vmscan: Throttle reclaim until some writeback completes if congested Mel Gorman
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