Messages in this thread | | | From | Weiping Zhang <> | Date | Fri, 5 Feb 2021 10:43:02 +0800 | Subject | Re: [RFC PATCH v2] taskstats: add /proc/taskstats to fetch pid/tgid status |
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On Fri, Feb 5, 2021 at 8:08 AM Balbir Singh <bsingharora@gmail.com> wrote: > > On Thu, Feb 04, 2021 at 10:37:20PM +0800, Weiping Zhang wrote: > > On Thu, Feb 4, 2021 at 6:20 PM Balbir Singh <bsingharora@gmail.com> wrote: > > > > > > On Sun, Jan 31, 2021 at 05:16:47PM +0800, Weiping Zhang wrote: > > > > On Wed, Jan 27, 2021 at 7:13 PM Balbir Singh <bsingharora@gmail.com> 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 <zwp10758@gmail.com> wrote: > > > > > > > > > > > > > > Hi David, > > > > > > > > > > > > > > Could you help review this patch ? > > > > > > > > > > > > > > thanks > > > > > > > > > > > > > > On Fri, Dec 18, 2020 at 1:24 AM Weiping Zhang > > > > > > > <zhangweiping@didiglobal.com> 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 <zhangweiping@didiglobal.com> > > > > > > > > > > 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? > > > > > This program just read every process's taskstats from kernel and do not > > any extra data calculation, that is to say it just test the time spend on > > these syscalls. It read data every 1 second, the output is delta time spend to > > read all 1000 or 10000 processes's taskstat. > > > > t1 = clock_gettime(); > > for_each_pid /* 1000 or 10000 */ > > read_pid_taskstat > > t2 = clock_gettime(); > > > > delta = t2 - t1. > > > > > > proccess-count netlink ioctl > > > > --------------------------------------------- > > > > 1000 0.004446851 0.001553733 > > > > 10000 0.047024986 0.023290664 > > > > Since netlink mode needs two syscall and ioctl mode needs one syscall > > the test result shows netlink cost double time compare to ioctl. > > So I want to add this interface to reduce the time cost by syscall. > > > > You can get the test script from: > > https://github.com/dublio/tools/tree/master/c/taskstat#test-the-performance-between-netlink-and-ioctl-mode > > > > Thanks > > > > Have you looked at the listener interface in taskstats, where one > can register to listen on a cpumask against all exiting processes? > > That provides a register once and listen and filter interface (based > on pids/tgids returned) and lets the task be done on exit as opposed > to polling for data. > That is a good feature to collect data async mode, now I want to collect those long-time running process's data in a fixed frequency, like iotop. So I try to reduce the overhead cost by these syscalls when I polling a lot of long-time running processes.
Thanks a ton
> Balbir Singh.
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