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From: Hao Li To: "Vlastimil Babka (SUSE)" Cc: Harry Yoo , Christoph Lameter , David Rientjes , Roman Gushchin , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, hu.shengming@zte.com.cn, Vinicius Costa Gomes Subject: Re: [PATCH v3 2/2] mm, slab: simplify returning slab in __refill_objects_node() Message-ID: References: <20260522-b4-refill-optimistic-return-v3-0-2ba78ec1c6ed@kernel.org> <20260522-b4-refill-optimistic-return-v3-2-2ba78ec1c6ed@kernel.org> <80d69c1c-a779-4402-af89-3be67b7f0e47@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <80d69c1c-a779-4402-af89-3be67b7f0e47@kernel.org> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 4132A180003 X-Stat-Signature: fcquhg6p8anep5ggixaeuuxm8yeru161 X-Rspam-User: X-HE-Tag: 1779709910-395336 X-HE-Meta: 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 6xuelI2X FVjjZgP9hvTN+FMCWazSoh9jF9fSEQ1jAwf9zW40ATSmGgI3GDrzVGsNpaNxRfsQwkTe+RD1zbFezQXX96GTAoPYovelqmV2craX06WGmK8rjCiLRP8Kfj7eg+DpSjzy33jhppjB1iIhmfy97KgVNQTbxJIfUz73ngidC1yfJyrlwOJCPz3BlgHVgzXR49UL3ymNq8Z7fkhlQobdzeG0iKs94+kamEO9fSCSTvlRRZ6ywnirMZZ8zK8NIXnioxVql0Yjt Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, May 25, 2026 at 09:15:49AM +0200, Vlastimil Babka (SUSE) wrote: > On 5/25/26 08:47, Hao Li wrote: > > On Fri, May 22, 2026 at 04:23:21PM +0200, Vlastimil Babka (SUSE) wrote: > >> When we return slabs to the partial list because we didn't fully refill > >> from them, we observe the min_partial limit when the returned slab is > >> empty, and discard it when over the limit. But it's unlikely for the > >> limit to be reached while we were refilling, and the worst outcome is to > >> have temporarily more free slabs on the list than necessary. > > > > Just wondering if the empty slabs temporarily exceed the limit and then some > > objects get allocated from them, would this lead to more fragmented slabs in > > the node partial list? > > I think since we're adding the slabs to tail and refill from head, it > shouldn't happen that easily. This makes sense! > Fragmenting is possible in general due to bad > luck, I doubt this change could make it noticeably worse. I ran a test and even though the data is pretty noisy, the length of the partial list indeed didn't really grow much. And after applying both patches, I can see some improvement (1~2%) in overall performance! Reviewed-by: Hao Li Tested-by: Hao Li -- Thanks, Hao