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[31.46.242.101]) by smtp.gmail.com with ESMTPSA id h4-20020a05600c350400b00402f713c56esm1165817wmq.2.2023.09.20.00.32.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Sep 2023 00:32:41 -0700 (PDT) Date: Wed, 20 Sep 2023 09:32:38 +0200 From: Ingo Molnar To: Steven Rostedt Cc: Thomas Gleixner , Linus Torvalds , John Paul Adrian Glaubitz , Peter Zijlstra , Matthew Wilcox , Ankur Arora , linux-kernel@vger.kernel.org, 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, 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, Geert Uytterhoeven , linux-m68k@lists.linux-m68k.org, Richard Weinberger , Anton Ivanov , Johannes Berg , linux-um@lists.infradead.org, Brian Cain , linux-hexagon@vger.kernel.org, Richard Henderson , Ivan Kokshaysky , Matt Turner , linux-alpha@vger.kernel.org Subject: Re: Arches that don't support PREEMPT Message-ID: References: <87cyyfxd4k.ffs@tglx> <87led2wdj0.ffs@tglx> <0e69f7df80dc5878071deb0d80938138d19de1d1.camel@physik.fu-berlin.de> <20230919134218.GA39281@noisy.programming.kicks-ass.net> <87pm2eui95.ffs@tglx> <20230919143816.1741760a@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230919143816.1741760a@gandalf.local.home> X-Rspamd-Queue-Id: 525C44000C X-Rspam-User: X-Stat-Signature: iumy4erf1an5cswq9ogxsaefgeyokjbb X-Rspamd-Server: rspam03 X-HE-Tag: 1695195163-635790 X-HE-Meta: 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 FbYPMdjk 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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: * Steven Rostedt wrote: > On Tue, 19 Sep 2023 20:31:50 +0200 > Thomas Gleixner wrote: > > > The removal of cond_resched() might cause latencies, but then I doubt > > that these museus pieces are used for real work :) > > We could simply leave the cond_resched() around but defined as nops for > everything but the "nostalgia club" to keep them from having any regressions. That's not a good idea IMO, it's an invitation for accelerated rate bitrot turning cond_resched() meaningless very quickly. We should remove cond_resched() - but probably not as the first step. They are conceptually independent of NEED_RESCHED_LAZY and we don't *have to* remove them straight away. By removing cond_resched() separately there's an easily bisectable point to blame for any longer latencies on legacy platforms, should any of them still be used with recent kernels. Thanks, Ingo