From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 05F36A932; Sun, 2 Feb 2025 07:22:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738480938; cv=none; b=STF5E5PPnSpw0q12cuBQLamPb7C8hglgVpHCyH4BpqeVzzwY/NNhEeLXvEEfhlw0HfeqfRcG2RZ4kCFbgpudIYd6cfogIdlJfa30RxQsiH6DfJbblpe+DwmAgEEBQ2hzXcYNTpxZgfg6HN4F8aV1UNZxqrt4bjclpHM9AYK2A9w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738480938; c=relaxed/simple; bh=2HQjkYIl3cLMQLG5F9U/gL5vESvDQQN09ZIPGSpFLHA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Yvbgp+aAn3v8f5xb1BfLBvwUtgTFrNuK2xZbwt4HoQumtJaRI/Bh5PXv0GfR3wemIj8qRc6siXjHkKL75eSj6vk8LbHh/8pvdiyAPRPzI+gjyfcOQKasUTzevGt078iuFQCNuxZLVZa4LAuhI1fMl2R6JEBvD9S1EfUp0XI9v3M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=m00Tytcw; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="m00Tytcw" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=kp2R2I4n2SrI5B0Gs6YVxJP2t+wd8P6NNyGAbLFTZGw=; b=m00TytcwXw3m/eh4wx2QP57IIO KDlRq87Ws9UqQuU802qi0q1wDPal06L6KlJyzis7q8VdzfqAGuxqY55BDuavRt6xp1cmrFdAmOdWk Ju6TIELAc2Zvb2l1Fc9B/qUf1CMlJZE8keYumrSgit1ASCivCgQ53LPqMlEx+99jts2vNgpiE54Jq X25b8mNhvj7hJBd8DrEASfsyOBhTrx/3zHp0gCrmO7t/+UGCnlxT7j/8k2c5q/b+dtx9Qnn/J6e3k ORcjw4cpFUc6g1Tk68Nl4vbGCDBWEbxhNuo+z6paJwpGNoFNKuPLpvxZ1YHLMqTDRZRKG0JA45wlC 34aaEigA==; 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250201222208.0b0d0f5c@batman.local.home> 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.