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([2409:8a28:e62:3990:257e:c5d2:cab0:ca98]) by smtp.gmail.com with ESMTPSA id o17-20020a639a11000000b0038160e4a2f7sm250359pge.48.2022.03.23.08.54.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Mar 2022 08:54:57 -0700 (PDT) Message-ID: Date: Wed, 23 Mar 2022 23:54:44 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [External] Re: [PATCH v2] psi: report zeroes for CPU full at the system level Content-Language: en-US To: peterz@infradead.org Cc: Johannes Weiner , corbet@lwn.net, mingo@redhat.com, surenb@google.com, ebiggers@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, songmuchun@bytedance.com, Martin Steigerwald References: <20220309111445.86484-1-zhouchengming@bytedance.com> From: Chengming Zhou In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/3/10 3:14 上午, Johannes Weiner wrote: > On Wed, Mar 09, 2022 at 07:14:45PM +0800, Chengming Zhou wrote: >> Martin find it confusing when look at the /proc/pressure/cpu output, >> and found no hint about that CPU "full" line in psi Documentation. >> >> % cat /proc/pressure/cpu >> some avg10=0.92 avg60=0.91 avg300=0.73 total=933490489 >> full avg10=0.22 avg60=0.23 avg300=0.16 total=358783277 >> >> The PSI_CPU_FULL state is introduced by commit e7fcd7622823 >> ("psi: Add PSI_CPU_FULL state"), which mainly for cgroup level, >> but also counted at the system level as a side effect. >> >> Naturally, the FULL state doesn't exist for the CPU resource at >> the system level. These "full" numbers can come from CPU idle >> schedule latency. For example, t1 is the time when task wakeup >> on an idle CPU, t2 is the time when CPU pick and switch to it. >> The delta of (t2 - t1) will be in CPU_FULL state. >> >> Another case all processes can be stalled is when all cgroups >> have been throttled at the same time, which unlikely to happen. >> >> Anyway, CPU_FULL metric is meaningless and confusing at the >> system level. So this patch will report zeroes for CPU full >> at the system level, and update psi Documentation accordingly. >> >> Fixes: e7fcd7622823 ("psi: Add PSI_CPU_FULL state") >> Reported-by: Martin Steigerwald >> Suggested-by: Johannes Weiner >> Signed-off-by: Chengming Zhou > > Acked-by: Johannes Weiner > > Peter, would you mind picking this up for 5.18? Hi Peter, ping... Maybe the subject should start with "sched/psi", to be easier to notice ;-) Thanks. > > Thanks!