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[2001:8b0:10b:1231::1]) by mx.google.com with ESMTPS id h9si1614431wmf.10.2019.01.29.02.44.45 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 29 Jan 2019 02:44:46 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of peterz@infradead.org designates 2001:8b0:10b:1231::1 as permitted sender) client-ip=2001:8b0:10b:1231::1; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=merlin.20170209 header.b=Jk0fptbw; spf=pass (google.com: best guess record for domain of peterz@infradead.org designates 2001:8b0:10b:1231::1 as permitted sender) smtp.mailfrom=peterz@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=/DYnSP8wwfkVagxlcXdbh9VOXn6NyWlZWTa5ybGjpLI=; b=Jk0fptbwefzDq9+8zgftkY20d 8S0HjEYx3W+J+CiaW3yCBRQi0gRLhDpQapl661tD+UD51GNxqwhk4DCEsUZTZO0URngSGCK5T59xD JtGj8ZWFL4Jt8tnkbUuNnyncF4lIH7sm7URnzzp9WO0be1AhK4U0uo8lmZy3mtvJPMwV9Rutb50Sv DVZ2ZTggkXUTqp2XPUldmoZJG04oFmB+wx66t18Imh0r+agjQTCJ0aK0nGIgFR9aCVHnHx969KoX0 bG7U89mBgq3HA5cZqmkgbLkeTbk2UYHcFEhwAAs7mfqs7H41qw4fuQGDYKzQ+KPu/p4uasxvQIGQh D0KFbAGpQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1goQsa-0000Kv-H3; Tue, 29 Jan 2019 10:44:32 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4EECB201EC171; Tue, 29 Jan 2019 11:44:31 +0100 (CET) Date: Tue, 29 Jan 2019 11:44:31 +0100 From: Peter Zijlstra To: Suren Baghdasaryan Cc: gregkh@linuxfoundation.org, tj@kernel.org, lizefan@huawei.com, hannes@cmpxchg.org, axboe@kernel.dk, dennis@kernel.org, dennisszhou@gmail.com, mingo@redhat.com, akpm@linux-foundation.org, corbet@lwn.net, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v3 5/5] psi: introduce psi monitor Message-ID: <20190129104431.GJ28467@hirez.programming.kicks-ass.net> References: <20190124211518.244221-1-surenb@google.com> <20190124211518.244221-6-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190124211518.244221-6-surenb@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Thu, Jan 24, 2019 at 01:15:18PM -0800, Suren Baghdasaryan wrote: > static void psi_update_work(struct work_struct *work) > { > struct delayed_work *dwork; > struct psi_group *group; > + bool first_pass = true; > + u64 next_update; > + u32 change_mask; > + int polling; > bool nonidle; > + u64 now; > > dwork = to_delayed_work(work); > group = container_of(dwork, struct psi_group, clock_work); > > + now = sched_clock(); > + > + mutex_lock(&group->update_lock); actually acquiring a mutex can take a fairly long while; would it not make more sense to take the @now timestanp _after_ it, instead of before?