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charset=us-ascii Content-Disposition: inline X-Rspamd-Queue-Id: 9051A100010 X-Stat-Signature: htdpphne9u38s9fsdms55c8ysjcpe3ai X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1771957593-306538 X-HE-Meta: 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 4k3dAKzj 7qSd+Fv2PTnmeGCrsFRil4hRJMdTSG86CgMx0BhUJhTHtCQcOrkXOnGnlHXkA1432+JubOarQ4QspU4GHbgdbFZ5MzcSN5mAu6/F9Q9XMgVa8/r45EPJZCFnZBQoHqevtYiDGOKHnsxzaN6Qc6c7pbGDo/LgJplrpzceQ800T3bSCk1CgWNkA3ZlXZzIiw0ABADJzK5HWCNS105Dp3FLlkKDR+bXwkihUj2SUvnyhO2E7BWR15Dayn5OjO94vS9zqKEhPbDbHxZgxMst2ysvjVOGxV/GiX+rxvxHNwba3KbhaSaUD+h0C6MxcsuylB85AWd5qejhjsfm61wnca9PgQKW35gCkBaNAgzid6oImQMsJVLFuUtyDdPHDSlLV2UxZjRiSvYpkB58vBFSGkvfEDKyZdu26ZS5KJsb4KzGSrXbJN2WrNPsSNbVlO/B9Ich2UHAsAlWJvQEut+2Mq9uSZKy34a5y3fEAunM7 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Feb 23, 2026 at 10:11:11AM +0100, Michal Hocko wrote: > On Fri 20-02-26 16:01:59, Marcelo Tosatti wrote: > > On Fri, Feb 20, 2026 at 06:58:10PM +0100, Vlastimil Babka wrote: > [...] > > > >> So if we can assume that workloads on isolated cpus make syscalls only > > > >> rarely, and when they do they can tolerate them being slower, I think the > > > >> "avoid sheaves on isolated cpus" would be the best way here. > > > > > > > > I am not sure its safe to assume that. Ask Gemini about isolcpus use > > > > cases and: > > > > > > I don't think it's answering the question about syscalls. But didn't read > > > too closely given the nature of it. > > > > People use isolcpus with all kinds of programs. > > > > > > For example, AF_XDP bypass uses system calls (and wants isolcpus): > > > > > > > > https://www.quantvps.com/blog/kernel-bypass-in-hft?srsltid=AfmBOoryeSxuuZjzTJIC9O-Ag8x4gSwjs-V4Xukm2wQpGmwDJ6t4szuE > > > > > > Didn't spot system calls mentioned TBH. > > > > I don't see why you want to reduce performance of applications that > > execute on isolcpus=, if you can avoid that. > > If you can avoid that by making performance bad for everybody else then > then it seems safer to sacrifice those workloads that are much more > special - i.e. cpu isolation. > -- > Michal Hocko > SUSE Labs Performance is not bad for everyone else: Without patchset: ================ [ 1188.050725] kmalloc_bench: Avg cycles per kmalloc: 159 With qpw patchset, CONFIG_QPW=n: ================================ [ 50.292190] kmalloc_bench: Avg cycles per kmalloc: 163 And its probably possible to remove those 4 cycles. Which makes reduction of performance of isolcpus not necessary.