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From: Dave Chinner <david@fromorbit.com>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: 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>,
	Matthew Wilcox <willy@infradead.org>,
	Michal Hocko <mhocko@suse.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: Wed, 22 Sep 2021 06:46:21 +1000	[thread overview]
Message-ID: <20210921204621.GY2361455@dread.disaster.area> (raw)
In-Reply-To: <20210920085436.20939-1-mgorman@techsingularity.net>

On Mon, Sep 20, 2021 at 09:54:31AM +0100, Mel Gorman wrote:
> Cc list similar to "congestion_wait() and GFP_NOFAIL" as they're loosely
> related.
> 
> This is a prototype series that removes all calls to congestion_wait
> in mm/ and deletes wait_iff_congested. It's not a clever
> implementation but congestion_wait has been broken for a long time
> (https://lore.kernel.org/linux-mm/45d8b7a6-8548-65f5-cccf-9f451d4ae3d4@kernel.dk/).
> Even if it worked, it was never a great idea. While excessive
> dirty/writeback pages at the tail of the LRU is one possibility that
> reclaim may be slow, there is also the problem of too many pages being
> isolated and reclaim failing for other reasons (elevated references,
> too many pages isolated, excessive LRU contention etc).
> 
> This series replaces the reclaim conditions with event driven ones
> 
> o If there are too many dirty/writeback pages, sleep until a timeout
>   or enough pages get cleaned
> o If too many pages are isolated, sleep until enough isolated pages
>   are either reclaimed or put back on the LRU
> o If no progress is being made, let direct reclaim tasks sleep until
>   another task makes progress
> 
> 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.

Got a git tree pointer so I can pull it into a test kernel so I can
see what impact it has on behaviour before I try to make sense of
the code?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  parent reply	other threads:[~2021-09-21 20:46 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-20  8:54 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
2021-09-22 12:16   ` Hillf Danton
2021-09-22 14:13     ` 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
2021-09-21 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
2021-09-20 19:51   ` Mel Gorman
2021-09-21 20:46 ` Dave Chinner [this message]
2021-09-22 17:52   ` Mel Gorman

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