On Thu, Feb 04, 2021 at 10:37:20PM +0800, Weiping Zhang wrote: > On Thu, Feb 4, 2021 at 6:20 PM Balbir Singh <bsinghar...@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 <bsinghar...@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 <zwp10...@gmail.com> > > > > > wrote: > > > > > > > > > > > > Hi David, > > > > > > > > > > > > Could you help review this patch ? > > > > > > > > > > > > thanks > > > > > > > > > > > > On Fri, Dec 18, 2020 at 1:24 AM Weiping Zhang > > > > > > <zhangweip...@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 <zhangweip...@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. Balbir Singh.
