From: Andrew Morton <akpm@linux-foundation.org>
To: Salvatore Dipietro <dipiets@amazon.it>
Cc: <linux-kernel@vger.kernel.org>, <hch@infradead.org>,
<abuehaze@amazon.com>, <alisaidi@amazon.com>,
<blakgeof@amazon.com>, <brauner@kernel.org>, <dgc@kernel.org>,
<dipietro.salvatore@gmail.com>, <djwong@kernel.org>,
<hannes@cmpxchg.org>, <jackmanb@google.com>,
<linux-fsdevel@vger.kernel.org>, <linux-mm@kvack.org>,
<linux-xfs@vger.kernel.org>, <mhocko@suse.com>,
<ritesh.list@gmail.com>, <rvvandan@amazon.com>,
<stable@vger.kernel.org>, <surenb@google.com>,
<vbabka@kernel.org>, <willy@infradead.org>, <ziy@nvidia.com>,
Vlastimil Babka <vbabka@suse.cz>,
David Hildenbrand <david@redhat.com>,
Christoph Hellwig <hch@lst.de>,
Brendan Jackman <brendan.jackman@linux.dev>
Subject: Re: [PATCH v4] mm/page_alloc: avoid direct compaction for costly __GFP_NORETRY allocations
Date: Sat, 5 Sep 2026 17:42:39 -0700 [thread overview]
Message-ID: <20260905174239.99e31515fabe220aa7d8e6fa@linux-foundation.org> (raw)
In-Reply-To: <20260904115629.3993331-1-dipiets@amazon.it>
On Fri, 4 Sep 2026 11:56:28 +0000 Salvatore Dipietro <dipiets@amazon.it> wrote:
> Commit 5d8edfb900d5 ("iomap: Copy larger chunks from userspace")
> introduced high-order folio allocations in the iomap buffered write
> path. When memory is fragmented, each failed costly-order allocation
> enters __alloc_pages_slowpath() which runs direct compaction and
> drain_all_pages(), causing a 0.38x throughput drop on PostgreSQL
> pgbench (simple-update) with 1024 clients on a 96-vCPU arm64 system.
Is there anything particularly unusual about this test case?
> Results (average of 3 runs, TPS):
>
> Config Avg TPS % vs Baseline
> baseline (no patch) 59,408 -
> With this patch 155,409 +161.6%
Is this back to pre-5d8edfb900d5 performance?
> Link: https://lore.kernel.org/all/20260403193535.9970-1-dipiets@amazon.it/T/#t [v1]
> Link: https://lore.kernel.org/linux-mm/20260420161404.642-1-dipiets@amazon.it/T/#u [v2]
> Link: https://lore.kernel.org/all/20260710143437.12379-1-dipiets@amazon.it/T/#u [v3]
> Fixes: 5d8edfb900d5 ("iomap: Copy larger chunks from userspace")
That's three years old. v6.10.
This is not good. Can you think of an exceptional reason why this took
so long to surface, or is it simply that our testing isn't good?
And thanks for fixing it.
AI review asked a few serious-looking questions:
https://sashiko.dev/#/patchset/20260904115629.3993331-1-dipiets@amazon.it
next prev parent reply other threads:[~2026-09-06 0:42 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-04 11:56 [PATCH v4] mm/page_alloc: avoid direct compaction for costly __GFP_NORETRY allocations Salvatore Dipietro
2026-09-04 14:11 ` Vlastimil Babka (SUSE)
2026-09-04 15:08 ` Zi Yan
2026-09-07 7:30 ` Vlastimil Babka (SUSE)
2026-09-09 2:33 ` Zi Yan
2026-09-09 8:51 ` Vlastimil Babka (SUSE)
2026-09-04 16:10 ` Johannes Weiner
2026-09-06 0:42 ` Andrew Morton [this message]
2026-09-06 23:05 ` Dave Chinner
2026-09-10 11:46 ` Salvatore Dipietro
2026-09-07 5:54 ` Christoph Hellwig
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