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Wed, 7 Oct 2026 09:01:34 -0400 (EDT) Date: Wed, 7 Oct 2026 14:01:33 +0100 From: Kiryl Shutsemau To: Andrew Morton Cc: Vlastimil Babka , Johannes Weiner , David Hildenbrand , Harry Yoo , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Zi Yan , Shakeel Butt , Usama Arif , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v2] mm: page_alloc: make defrag_mode retries follow the promoted order Message-ID: References: <20261006091815.897133-1-kirill@shutemov.name> <20261006164122.ea9a673b336b8ac74725c35c@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261006164122.ea9a673b336b8ac74725c35c@linux-foundation.org> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 5B483180011 X-Rspam-User: X-Stat-Signature: 76kkqq1sx4xxdci1zug8q8sz9td9ncy4 X-HE-Tag: 1791378098-326795 X-HE-Meta: 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 3NlVpoHj 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Oct 06, 2026 at 04:41:22PM -0700, Andrew Morton wrote: > On Tue, 6 Oct 2026 10:18:13 +0100 Kiryl Shutsemau wrote: > > > From: "Kiryl Shutsemau (Meta)" > > > > Since commit 7e8756d7ad22 ("mm: page_alloc: fix non-movable reclaim > > storm in defrag_mode"), direct reclaim and compaction for non-movable > > requests under defrag_mode run at pageblock_order, to produce the whole > > blocks that ALLOC_NOFRAGMENT needs. The retry decisions that follow > > still use the request order. An order-0 request can therefore retry > > indefinitely without ever reaching the ALLOC_NOFRAGMENT fallback: > > > > ... > > > > In a VM reproducer (32G, defrag_mode, inode churn under memory.low): > > > > before after > > should_reclaim_retry() calls 63M 293k > > peak memory pressure (PSI some avg10) 99% 12% > > > > File creation runs 5.7x faster. > > > Fixes: 7e8756d7ad22 ("mm: page_alloc: fix non-movable reclaim storm in defrag_mode") > > Cc: stable@vger.kernel.org > > Assisted-by: LLM > > Signed-off-by: Kiryl Shutsemau (Meta) > > --- > > v2: > > - keep the compaction priority floor and the COMPACT_SUCCESS retry > > limit on the request order, so non-costly requests still escalate to > > SYNC_FULL before falling back (Harry Yoo, Johannes Weiner) > > - compute the promoted order once in __alloc_pages_slowpath() and pass > > it to direct reclaim, direct compaction and the retry helpers, instead > > of each of them deriving it (Harry Yoo) > > Thanks. That's a fairly large update. v2 diff is below. > > Are we sure about cc:stable? Or even 7.3-rcX? It's a pretty big > change. I think defrag_mode is not widely used. Maybe only in Meta. What about keeping cc:stable, but only submit it to Linus for v7.4-rc1? By the time we would have the patch battle-tested in the fleet. -- Kiryl Shutsemau / Kirill A. Shutemov