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h=Date:From:To:Cc:Subject:In-Reply-To:References; b=DH+YNIWar6wt1hdxQ72+7q6esIgjvBDieMtYb75WVM9L5FOTr3Ca3mSeY5LpHYALu SrooTcOzf/OGvsFOC7HuJGILmvO8Epx7K459+4ZeWUlKIdeHNcjeY8SafIc1lx/13r R/+GTdeReqy0Af0lnKAmyMndnjwjcW8qNm/zpDZQ= Date: Sat, 5 Sep 2026 17:42:39 -0700 From: Andrew Morton To: Salvatore Dipietro Cc: , , , , , , , , , , , , , , , , , , , , , , Vlastimil Babka , David Hildenbrand , Christoph Hellwig , Brendan Jackman Subject: Re: [PATCH v4] mm/page_alloc: avoid direct compaction for costly __GFP_NORETRY allocations Message-Id: <20260905174239.99e31515fabe220aa7d8e6fa@linux-foundation.org> In-Reply-To: <20260904115629.3993331-1-dipiets@amazon.it> References: <20260904115629.3993331-1-dipiets@amazon.it> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: EFE64C0007 X-Stat-Signature: hxbpwho158jnzn7emw1bnt6x7pqcoxeg X-Rspam-User: X-HE-Tag: 1788655361-939832 X-HE-Meta: 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 P65s9DxO IjkHNRzMoy0iwxB6ADFM+8nW5Yyg8RBDap+pLA5ZxE5/rlBVuCGleQY5Jixxn3YMb+dHI+AbT/E7t7JPgzc8eaidgpDH9KJ60W1Ov/bAqzuxQ8gTEhh4xnJZiVAMceUVPtzkn9naU2zRiazFmwrzUt3oiE9+ijjqb82YpYqNZDqNVbcGLCXJ6lwPZESK/dsshQtWGvFdc+e/kBfit7Mkpj/KddZmTfXgkm8O+e1UMVVi71pjAodgDo4S8+AopwUaIB9NbydYb271na1dWKLHeVXY3PHgAxOAWfLTIhVRuTo/qy12nridKJw77PDWPF5Cb1dqi137W1YBps0ne0c2Sy/gB5gH2yhDMI44rGRQ7VkNBj7ipXChLOgpPkSAshKoOZg0kQxvm5CmVe5jsBhXcpUuJRbqwq7B+edCLvBBGX8LimvhEWCJtVlTBiNW3DF/Jhs7T0Ylb2mDqVu0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 4 Sep 2026 11:56:28 +0000 Salvatore Dipietro 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