From: Matthew Wilcox <willy@infradead.org>
To: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Boris Burkov <boris@bur.io>,
akpm@linux-foundation.org, linux-btrfs@vger.kernel.org,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
kernel-team@fb.com, wqu@suse.com, mhocko@kernel.org,
muchun.song@linux.dev, roman.gushchin@linux.dev,
hannes@cmpxchg.org
Subject: Re: [PATCH v3 2/4] mm: add vmstat for cgroup uncharged pages
Date: Wed, 20 Aug 2025 00:46:43 +0100 [thread overview]
Message-ID: <aKUM49I-4D24MmwZ@casper.infradead.org> (raw)
In-Reply-To: <tw5qydmgv35v63lhqgl7zbjmgwxm2cujqdjq3deicdz2k26ymh@mnxhz43e6jwl>
On Tue, Aug 19, 2025 at 08:53:59AM -0700, Shakeel Butt wrote:
> My initial thinking was based on Qu's original proposal which was using
> root memcg where there will not be any difference between accounted
> file pages and system wide file pages. However with Boris's change, we
> can actually get the estimate, as you pointed out, by subtracting the
> number of accounted file pages from system wide number of file pages.
>
> However I still think we should keep this new metric because of
> performance reason. To get accounted file pages, we need to read
> memory.stat of the root memcg which can be very expensive. Basically it
> may have to flush the rstat update trees on all the CPUs on the system.
> Since this new metric will be used to calculate system overhead, the
> high cost will limit how frequently a user can query the latest stat.
OK, but couldn't we make that argument for anything else? Like slab,
say. Why's "file" memory different?
next prev parent reply other threads:[~2025-08-19 23:46 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-19 0:36 [PATCH v3 0/4] introduce uncharged file mapped folios Boris Burkov
2025-08-19 0:36 ` [PATCH v3 1/4] mm/filemap: add AS_UNCHARGED Boris Burkov
2025-08-19 2:46 ` Matthew Wilcox
2025-08-19 3:57 ` Boris Burkov
2025-08-20 22:06 ` Klara Modin
2025-08-20 22:22 ` Shakeel Butt
2025-08-20 22:52 ` Boris Burkov
2025-08-20 23:15 ` Klara Modin
2025-08-20 23:53 ` Shakeel Butt
2025-08-21 19:37 ` Shakeel Butt
2025-08-19 0:36 ` [PATCH v3 2/4] mm: add vmstat for cgroup uncharged pages Boris Burkov
2025-08-19 2:50 ` Matthew Wilcox
2025-08-19 4:05 ` Boris Burkov
2025-08-19 15:53 ` Shakeel Butt
2025-08-19 23:46 ` Matthew Wilcox [this message]
2025-08-20 1:25 ` Shakeel Butt
2025-08-20 13:19 ` Matthew Wilcox
2025-08-20 16:21 ` Shakeel Butt
2025-08-19 0:36 ` [PATCH v3 3/4] btrfs: set AS_UNCHARGED on the btree_inode Boris Burkov
2025-08-19 0:36 ` [PATCH v3 4/4] memcg: remove warning from folio_lruvec Boris Burkov
2025-08-19 2:41 ` Matthew Wilcox
2025-08-19 5:20 ` Andrew Morton
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