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    SubjectRe: [RFC PATCH v2] taskstats: add /proc/taskstats to fetch pid/tgid status
    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?

    Balbir Singh


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