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From: Mel Gorman <mgorman@suse.de>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com
Subject: Re: [PATCH] mm: don't wake kswapd prematurely when watermark boosting is disabled
Date: Tue, 20 Oct 2020 21:33:31 +0100	[thread overview]
Message-ID: <20201020203331.GB32041@suse.de> (raw)
In-Reply-To: <20201020175833.397286-1-hannes@cmpxchg.org>

On Tue, Oct 20, 2020 at 01:58:33PM -0400, Johannes Weiner wrote:
> On 2-node NUMA hosts we see bursts of kswapd reclaim and subsequent
> pressure spikes and stalls from cache refaults while there is plenty
> of free memory in the system.
> 
> Usually, kswapd is woken up when all eligible nodes in an allocation
> are full. But the code related to watermark boosting can wake kswapd
> on one full node while the other one is mostly empty. This may be
> justified to fight fragmentation, but is currently unconditionally
> done whether watermark boosting is occurring or not.
> 
> In our case, many of our workloads' throughput scales with available
> memory, and pure utilization is a more tangible concern than trends
> around longer-term fragmentation. As a result we generally disable
> watermark boosting.
> 
> Wake kswapd only woken when watermark boosting is requested.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

This makes sense to the extent that I would support adding

Fixes: 1c30844d2dfe ("mm: reclaim small amounts of memory when an external fragmentation event occurs")

With or without that;

Acked-by: Mel Gorman <mgorman@suse.de>

-- 
Mel Gorman
SUSE Labs


      reply	other threads:[~2020-10-20 20:33 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-20 17:58 [PATCH] mm: don't wake kswapd prematurely when watermark boosting is disabled Johannes Weiner
2020-10-20 20:33 ` Mel Gorman [this message]

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