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t=1671024785; bh=pgq56pmJqqIVUdDDmdTZvjimbzCmSvIS6vFQXH1iDe0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hp95v2iTs3ZfzAJUGHlUUIR5CoSDV1/wazuzI3W1ThIJDliqJJ57EiBpic2y4Pl8H 7u15iFp4GHluRmVk3LCOFGGLVvTvGVRMriKwtjhoZJ7spggCDrZxtk+xGnrxHG+xTq JLY2FPLl7x36mbOOYSIRdw4v8kU+O2ZIc9Z+Wgx18QF/Dl7iWGlk+swxrOnTuQ2q5O JhgNoU4ABB6g8uS1RrQYOkexXo4PJnHykNfyB+f7xGY2fW/QGUfQqG1LJmpnWQcQma rA8pu/Ek8vYx5bGVeQzUkxWQicQ3aj57oxvsqPZ6nwKXWyEk/Hrgzu/QGCXuMj3V4r wrPHmjrmNGXMQ== Date: Wed, 14 Dec 2022 14:33:02 +0100 From: Frederic Weisbecker To: Marcelo Tosatti Cc: atomlin@redhat.com, cl@linux.com, tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org, pauld@redhat.com, neelx@redhat.com, oleksandr@natalenko.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v9 3/5] mm/vmstat: manage per-CPU stats from CPU context when NOHZ full Message-ID: <20221214133302.GA1931356@lothringen> References: <20221206161826.698593151@redhat.com> <20221206162416.474800121@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221206162416.474800121@redhat.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 4178F10001B X-Stat-Signature: j6wfpsgnaojbqinrczo1bx3qmdsp8qbx X-HE-Tag: 1671024788-467969 X-HE-Meta: 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 vGi0rrre 1oaNBGDSaPRz9qVOThdpH6unlzK18NvRQek4I 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 Tue, Dec 06, 2022 at 01:18:29PM -0300, Marcelo Tosatti wrote: > static inline void vmstat_mark_dirty(void) > { > + int cpu = smp_processor_id(); > + > + if (tick_nohz_full_cpu(cpu) && !this_cpu_read(vmstat_dirty)) { > + struct delayed_work *dw; > + > + dw = &per_cpu(vmstat_work, cpu); > + if (!delayed_work_pending(dw)) { > + unsigned long delay; > + > + delay = round_jiffies_relative(sysctl_stat_interval); > + queue_delayed_work_on(cpu, mm_percpu_wq, dw, delay); Currently the vmstat_work is flushed on cpu_hotplug (CPUHP_AP_ONLINE_DYN). vmstat_shepherd makes sure to not rearm it afterward. But now it looks possible for the above to do that mistake? > + } > + } > this_cpu_write(vmstat_dirty, true); > } > @@ -2009,6 +2028,10 @@ static void vmstat_shepherd(struct work_ > for_each_online_cpu(cpu) { > struct delayed_work *dw = &per_cpu(vmstat_work, cpu); > > + /* NOHZ full CPUs manage their own vmstat flushing */ > + if (tick_nohz_full_cpu(smp_processor_id())) It should be the remote CPU instead of the current one. Thanks. > + continue; > + > if (!delayed_work_pending(dw) && per_cpu(vmstat_dirty, cpu)) > queue_delayed_work_on(cpu, mm_percpu_wq, dw, 0); >