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[121.45.171.254]) by smtp.gmail.com with ESMTPSA id 123sm5363785pfd.91.2021.02.04.02.20.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Feb 2021 02:20:23 -0800 (PST) Date: Thu, 4 Feb 2021 21:20:20 +1100 From: Balbir Singh To: Weiping Zhang Cc: sblbir@amazon.com, davem@davemloft.net, Linux Kernel Mailing List Subject: Re: [RFC PATCH v2] taskstats: add /proc/taskstats to fetch pid/tgid status Message-ID: <20210204102020.GA286763@balbir-desktop> References: <20201217170009.GA29186@192.168.3.9> <20210127111346.GB59838@balbir-desktop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jan 31, 2021 at 05:16:47PM +0800, Weiping Zhang wrote: > On Wed, Jan 27, 2021 at 7:13 PM Balbir Singh wrote: > > > > On Fri, Jan 22, 2021 at 10:07:50PM +0800, Weiping Zhang wrote: > > > Hello Balbir Singh, > > > > > > Could you help review this patch, thanks > > > > > > On Mon, Dec 28, 2020 at 10:10 PM Weiping Zhang wrote: > > > > > > > > Hi David, > > > > > > > > Could you help review this patch ? > > > > > > > > thanks > > > > > > > > On Fri, Dec 18, 2020 at 1:24 AM Weiping Zhang > > > > wrote: > > > > > > > > > > If a program needs monitor lots of process's status, it needs two > > > > > syscalls for every process. The first one is telling kernel which > > > > > pid/tgid should be monitored by send a command(write socket) to kernel. > > > > > The second one is read the statistics by read socket. This patch add > > > > > a new interface /proc/taskstats to reduce two syscalls to one ioctl. > > > > > The user just set the target pid/tgid to the struct taskstats.ac_pid, > > > > > then kernel will collect statistics for that pid/tgid. > > > > > > > > > > Signed-off-by: Weiping Zhang > > > > Could you elaborate on the overhead your seeing for the syscalls? I am not > > in favour of adding new IOCTL's. > > > > Balbir Singh. > > Hello Balbir Singh, > > Sorry for late reply, > > I do a performance test between netlink mode and ioctl mode, > monitor 1000 and 10000 sleep processes, > the netlink mode cost more time than ioctl mode, that is to say > ioctl mode can save some cpu resource and has a quickly reponse > especially when monitor lot of process. > > proccess-count netlink ioctl > --------------------------------------------- > 1000 0.004446851 0.001553733 > 10000 0.047024986 0.023290664 > > you can get the test demo code from the following link > https://github.com/dublio/tools/tree/master/c/taskstat > Let me try it out, I am opposed to adding the new IOCTL interface you propose. How frequently do you monitor this data and how much time in spent in making decision on the data? I presume the data mentioned is the cost per call in seconds? Balbir Singh