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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1teUIy-0000000GkyH-1NvM; Sun, 02 Feb 2025 07:22:08 +0000 Date: Sun, 2 Feb 2025 07:22:08 +0000 From: Matthew Wilcox To: Steven Rostedt Cc: Linus Torvalds , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , 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, juri.lelli@redhat.com, vincent.guittot@linaro.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 , Vineeth Pillai , Suleiman Souhlal , Ingo Molnar , Clark Williams , bigeasy@linutronix.de, daniel.wagner@suse.com, joseph.salisbury@oracle.com, broonie@gmail.com Subject: Re: [RFC][PATCH 1/2] sched: Extended scheduler time slice Message-ID: References: <20250131225837.972218232@goodmis.org> <20250131225942.365475324@goodmis.org> <20250201180810.1faf4906@batman.local.home> <20250201222208.0b0d0f5c@batman.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250201222208.0b0d0f5c@batman.local.home> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 426A91C000F X-Stat-Signature: y1f765tiknbd7331q3x4q5tzbyb7tweo X-Rspam-User: X-HE-Tag: 1738480937-52343 X-HE-Meta: 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 W545tA6Q AYuIlHKCWlxjk9yDFkO3gDhB59dBS81zE9A4g039Lym57g2+wkDMU3da2A9rrVvAot2m5RgAYIXuTU0ctZHakG9FITSukwfHTzEK9YLEojIq4ZeqZzYmFJulgAoUr2zDV9wA524ZN9l3yu1htWhgd4QWJMyhdVXJC9bBicwCedaGOfArfg3corCv26TvLhlaSWEiHwY+HF813IiBU00J7w+RdQ45xiAEIn2YLi1wBwzt8zwCQDv6lSUl0tDp2G+vfK7rjilPw1OeCETdMBtno38MeKI7aO7c1QpDnssKK0crbH7Y= 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 Sat, Feb 01, 2025 at 10:22:08PM -0500, Steven Rostedt wrote: > And before seeing Peter's use of yield(), I was reluctant to use it for > the very same reasons you mentioned above. In my test programs, I was > simply using getuid(), as that was one of the quickest syscalls. Is getuid() guaranteed to issue a syscall? It feels like the kind of information that a tricksy libc could cache. Traditionally, I think we've used getppid() as the canonical "very cheap syscall" as no layer can cache that information.