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Peter Anvin" , Ingo Molnar , juri.lelli@redhat.com, vincent.guittot@linaro.org, "Matthew Wilcox (Oracle)" , mgorman@suse.de, "Peter Zijlstra (Intel)" , Steven Rostedt , Jon Grimm , Bharata B Rao , raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, Linus Torvalds Subject: Re: [PATCH v2 7/9] sched: define TIF_ALLOW_RESCHED In-Reply-To: <39998df7-8882-43ae-8c7e-936c24eb4041@app.fastmail.com> References: <20230830184958.2333078-1-ankur.a.arora@oracle.com> <20230830184958.2333078-8-ankur.a.arora@oracle.com> <39998df7-8882-43ae-8c7e-936c24eb4041@app.fastmail.com> Date: Tue, 19 Sep 2023 11:20:13 +0200 Message-ID: <87pm2ewmcy.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: 075CE12001B X-Rspam-User: X-Stat-Signature: pzm5swth9ibgpq1riqzwbkqg9tbqfb8k X-Rspamd-Server: rspam03 X-HE-Tag: 1695115215-833407 X-HE-Meta: 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 YTfq7CJ3 BRCMBdA7V4zMveaJq7WIgHCn+JdiUpPeKnPIQw0tbo1lsbOgGl4DVoEEjSsr8xwcQAmVpgE1Z4Q0+9VbGd65Lt/DgZyx4bXsn5qjTdJHCG7p8Sg6IklN6/4lJEw== 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: On Mon, Sep 18 2023 at 20:21, Andy Lutomirski wrote: > On Wed, Aug 30, 2023, at 11:49 AM, Ankur Arora wrote: > Why do we support anything other than full preempt? I can think of > two reasons, neither of which I think is very good: > > 1. Once upon a time, tracking preempt state was expensive. But we fixed that. > > 2. Folklore suggests that there's a latency vs throughput tradeoff, > and serious workloads, for some definition of serious, want > throughput, so they should run without full preemption. It's absolutely not folklore. Run to completion is has well known benefits as it avoids contention and avoids the overhead of scheduling for a large amount of scenarios. We've seen that painfully in PREEMPT_RT before we came up with the concept of lazy preemption for throughput oriented tasks. Thanks, tglx