linux-kernel - Re: [PATCH 0/2] Support kshrinkd

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Message-ID: <ZdOG-135dLP0IeU8@casper.infradead.org>
Date: Mon, 19 Feb 2024 16:51:07 +0000
From: Matthew Wilcox <willy@...radead.org>
To: lipeifeng@...o.com
Cc: akpm@...ux-foundation.org, david@...hat.com, osalvador@...e.de,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Support kshrinkd

On Mon, Feb 19, 2024 at 10:17:01PM +0800, lipeifeng@...o.com wrote:
> 'commit 6d4675e60135 ("mm: don't be stuck to rmap lock on reclaim path")'
> The above patch would avoid reclaim path to stuck rmap lock.
> But it would cause some folios in LRU not sorted by aging because
> the contended-folios in rmap_walk would be putbacked to the head of LRU
> during shrink_folio_list even if the folios are very cold.
> 
> The patchset setups new kthread:kshrinkd to reclaim the contended-folio
> in rmap_walk when shrink_folio_list, to avoid to break the rules of LRU.

Patch 1/2 didn't make it to my inbox or to lore.  But you should talk
about the real world consequences of this in the cover letter.  What do
we observe if this problem happens?  How much extra performance will we
gain by applying this patch?