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b=WmiafaaUd3N0urhZWm8ej60bzApAWQpt38JX2BoGr8OV3tszUuCJojKJMQmYGdJ7W V9ZbwFBsf3RvRRBvf64aM99RzGfnI6VWkyivf4ZCXOhHJrOyJT1wo6kpxeMJIK0Pmw O7H3J/IumMBFvtMEh5bfxgrIpVQ0tPc7ggQzTNSnbh3/hzml5wwraMlQ7GFkUt6CMo vPXRZ+fzEvf6PqDOraPeM+pWGxu0R/MO6kMV39rYN6HkXH3aaB5DTR8LjuqgabY7jh cP8GCa9K2RzX+qioulCI1ELzbTJD/VWY0bFe5y0mj7qmsdOijRN+Sp8gAcUgJDz4IT NWvu6F0HYsBaQ== Message-ID: Date: Mon, 9 Mar 2026 10:52:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/4] Introduce QPW for per-cpu operations To: Leonardo Bras , Marcelo Tosatti Cc: Michal Hocko , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Leonardo Bras , Thomas Gleixner , Waiman Long , Boqun Feng , Frederic Weisbecker References: <20260206143430.021026873@redhat.com> From: "Vlastimil Babka (SUSE)" Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 9004B100002 X-Rspamd-Server: rspam07 X-Stat-Signature: tofgms4oonwz7hwt9dndqeeegg5ts95d X-Rspam-User: X-HE-Tag: 1773049982-292554 X-HE-Meta: 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 56pApvaa uInA9VM9mkOwECsAVHC5srwVDSCjonA0kd916d9KhXA3FHOjA0K0oK90IEjjYXd4klaRK7Iavv8O1GBElhHt3r0oSaEjj01BIxzPDid7Tu9+FiqxGumjLeb/Figb6FP8PxkcTilXfFblpUHVURkwUxW+HjmCt6K1Ah2dBj+v8yrtTBFwgBLgj/zjxel8/0qhy3s5VQDMJFj+uDOSm2hcpwiWIQysVL5Pp0bRxiLW68FfEcRP2OzGjUPUMC+gSwJ/CQfRNISc5fj5mwelKHMiB5IHdOKBraUvK+b7wY9jMDidSqdvI5clu3s0f2dMnyoDlY0EivfAuF1QB8bY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/8/26 18:41, Leonardo Bras wrote: > Hi Marcelo, > > Great, hiding migrate_disable under the static branch is the best scenario. > > I wonder why we spend 2 cycles on the static branches, though, should be > close to nothing unless the branch predictor is too busy already. Well, we AFAIK static branches are runtime patched to non-conditional jumps or nops, so there's nothing left for the branch predictor to do. Or maybe I misunderstand your comment. It does however increase code footprint and thus instruction cache usage, so maybe that's an effect of that. > can always try to optimize in a different way. > > Thanks for the effort on this! > Leo