linux-kernel - Re: [PATCH v7] mm: shrink skip folio mapped by an exiting process

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Message-Id: <20240709142312.372b20d49c6a97ecd2cd9904@linux-foundation.org>
Date: Tue, 9 Jul 2024 14:23:12 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Zhiguo Jiang <justinjiang@...o.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, Barry Song
 <baohua@...nel.org>, David Hildenbrand <david@...hat.com>, Matthew Wilcox
 <willy@...radead.org>, opensource.kernel@...o.com
Subject: Re: [PATCH v7] mm: shrink skip folio mapped by an exiting process

On Tue,  9 Jul 2024 20:31:15 +0800 Zhiguo Jiang <justinjiang@...o.com> wrote:

> The releasing process of the non-shared anonymous folio mapped solely by
> an exiting process may go through two flows: 1) the anonymous folio is
> firstly is swaped-out into swapspace and transformed into a swp_entry
> in shrink_folio_list; 2) then the swp_entry is released in the process
> exiting flow. This will result in the high cpu load of releasing a
> non-shared anonymous folio mapped solely by an exiting process.
> 
> When the low system memory and the exiting process exist at the same
> time, it will be likely to happen, because the non-shared anonymous
> folio mapped solely by an exiting process may be reclaimed by
> shrink_folio_list.
> 
> This patch is that shrink skips the non-shared anonymous folio solely
> mapped by an exting process and this folio is only released directly in
> the process exiting flow, which will save swap-out time and alleviate
> the load of the process exiting. 

It would be helpful to provide some before-and-after runtime
measurements, please.  It's a performance optimization so please let's
see what effect it has.