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[209.85.208.41]) by smtp.gmail.com with ESMTPSA id u4-20020a1709063b8400b009c624c55a7dsm16722ejf.199.2023.10.26.11.50.51 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 26 Oct 2023 11:50:51 -0700 (PDT) Received: by mail-ed1-f41.google.com with SMTP id 4fb4d7f45d1cf-540c54944c4so2555750a12.1 for ; Thu, 26 Oct 2023 11:50:51 -0700 (PDT) X-Received: by 2002:aa7:d352:0:b0:541:1e0d:b56f with SMTP id m18-20020aa7d352000000b005411e0db56fmr2544458edr.12.1698346251196; Thu, 26 Oct 2023 11:50:51 -0700 (PDT) MIME-Version: 1.0 References: <20231025235413.597287e1@gandalf.local.home> <20231026105944.GJ33965@noisy.programming.kicks-ass.net> <20231026071413.4ed47b0e@gandalf.local.home> In-Reply-To: From: Linus Torvalds Date: Thu, 26 Oct 2023 08:50:32 -1000 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [POC][RFC][PATCH v2] sched: Extended Scheduler Time Slice To: Mathieu Desnoyers Cc: Steven Rostedt , Peter Zijlstra , LKML , Thomas Gleixner , Ankur Arora , linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, willy@infradead.org, mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, jgross@suse.com, andrew.cooper3@citrix.com, Joel Fernandes , Youssef Esmat , Vineeth Pillai , Suleiman Souhlal , Ingo Molnar , Daniel Bristot de Oliveira Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 7813B2000E X-Stat-Signature: rua7qg8uwz3uz74ngrcymnu8bthh6zxn X-Rspam-User: X-HE-Tag: 1698346254-63193 X-HE-Meta: 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 UhGcv2uh 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 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 Thu, 26 Oct 2023 at 08:36, Mathieu Desnoyers wrote: > > > asm volatile("xchg %b0,%1" > > which has an implicit lock prefix (xchg with a memory operand is a > special-case): Yeah, this is why we do "percpu_xchg()" - which does not want locked semantics - as a "cmpxchg" loop. Steven, check out arch/x86/include/asm/percpu.h for a rough implementation of a 'xchg()' without SMP coherency, just cpu-local one (ie atomic wrt being preempted by the kernel, but not atomic wrt other CPU's accessing the same variable concurrently) Linus