* Andrea Righi <arighi@xxxxxxxxxxx> [2011-02-22 18:12:51]: > Currently the blkio.throttle controller only support synchronous IO requests. > This means that we always look at the current task to identify the "owner" of > each IO request. > > However dirty pages in the page cache can be wrote to disk asynchronously by > the per-bdi flusher kernel threads or by any other thread in the system, > according to the writeback policy. > > For this reason the real writes to the underlying block devices may > occur in a different IO context respect to the task that originally > generated the dirty pages involved in the IO operation. This makes the > tracking and throttling of writeback IO more complicate respect to the > synchronous IO from the blkio controller's perspective. > > The same concept is also valid for anonymous pages involed in IO operations > (swap). > > This patch allow to track the cgroup that originally dirtied each page in page > cache and each anonymous page and pass these informations to the blk-throttle > controller. These informations can be used to provide a better service level > differentiation of buffered writes swap IO between different cgroups. > > Testcase > ======== > - create a cgroup with 1MiB/s write limit: > # mount -t cgroup -o blkio none /mnt/cgroup > # mkdir /mnt/cgroup/foo > # echo 8:0 $((1024 * 1024)) > /mnt/cgroup/foo/blkio.throttle.write_bps_device > > - move a task into the cgroup and run a dd to generate some writeback IO > > Results: > - 2.6.38-rc6 vanilla: > $ cat /proc/$$/cgroup > 1:blkio:/foo > $ dd if=/dev/zero of=zero bs=1M count=1024 & > $ dstat -df > --dsk/sda-- > read writ > 0 19M > 0 19M > 0 0 > 0 0 > 0 19M > ... > > - 2.6.38-rc6 + blk-throttle writeback IO control: > $ cat /proc/$$/cgroup > 1:blkio:/foo > $ dd if=/dev/zero of=zero bs=1M count=1024 & > $ dstat -df > --dsk/sda-- > read writ > 0 1024 > 0 1024 > 0 1024 > 0 1024 > 0 1024 > ... > Thanks for looking into this, further review follows. -- Three Cheers, Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>