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Date: Sat, 4 Apr 2020 10:31:16 +0800 From: Yafang Shao <laoar.shao@...il.com> To: Johannes Weiner <hannes@...xchg.org> Cc: Peter Zijlstra <peterz@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Daniel Drake <drake@...lessm.com>, Suren Baghdasaryan <surenb@...gle.com> Subject: Re: [PATCH] psi: fix randomized calculation in record_times() On Fri, Apr 3, 2020 at 11:20 PM Johannes Weiner <hannes@...xchg.org> wrote: > > On Fri, Apr 03, 2020 at 04:55:25AM -0400, Yafang Shao wrote: > > @@ -690,7 +690,10 @@ static void psi_group_change(struct psi_group *group, int cpu, > > */ > > write_seqcount_begin(&groupc->seq); > > > > - record_times(groupc, cpu, false); > > + if (groupc->total_tasks) > > + record_times(groupc, cpu, false); > > + else > > + groupc->state_start = cpu_clock(cpu); > > This change appears is a no-op. If there are no tasks, > groupc->state_mask is 0, and the only thing record_times() does is > > groupc->state_start = cpu_clock(cpu); > > Did you encounter actual problems, or are you just reading the code? No real issues. Just reading the code and found it looks like a little weird. But as you explained that state_mask can also guarantee it then we don't need to make this change. Thanks for the explanation. Thanks Yafang
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