On Sun, Apr 01, 2012 at 09:46:06AM +0530, Suresh Jayaraman wrote: > On 03/28/2012 05:43 PM, Fengguang Wu wrote: > > Here is one possible solution to "buffered write IO controller", based on Linux > > v3.3 > > > > git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux.git buffered-write-io-controller > > > > The implementation looks unbelievably simple. I ran a few tests > (throttling) and I found it working well generally. Thanks for test it out :) > > Features: > > - support blkio.weight > > - support blkio.throttle.buffered_write_bps > > > > Possibilities: > > - it's trivial to support per-bdi .weight or .buffered_write_bps > > > > Pros: > > 1) simple > > 2) virtually no space/time overheads > > 3) independent of the block layer and IO schedulers, hence > > 3.1) supports all filesystems/storages, eg. NFS/pNFS, CIFS, sshfs, ... > > 3.2) supports all IO schedulers. One may use noop for SSDs, inside virtual machines, over iSCSI, etc. > > > > Cons: > > 1) don't try to smooth bursty IO submission in the flusher thread (*) > > 2) don't support IOPS based throttling > > 3) introduces semantic differences to blkio.weight, which will be > > - working by "bandwidth" for buffered writes > > - working by "device time" for direct IO > > There is a chance that this semantic difference might confuse users. Yeah. > > (*) Maybe not a big concern, since the bursties are limited to 500ms: if one dd > > is throttled to 50% disk bandwidth, the flusher thread will be waking up on > > every 1 second, keep the disk busy for 500ms and then go idle for 500ms; if > > throttled to 10% disk bandwidth, the flusher thread will wake up on every 5s, > > keep busy for 500ms and stay idle for 4.5s. > > > > The test results included in the last patch look pretty good in despite of the > > simple implementation. > > > > [PATCH 1/6] blk-cgroup: move blk-cgroup.h in include/linux/blk-cgroup.h > > [PATCH 2/6] blk-cgroup: account dirtied pages > > [PATCH 3/6] blk-cgroup: buffered write IO controller - bandwidth weight > > [PATCH 4/6] blk-cgroup: buffered write IO controller - bandwidth limit > > [PATCH 5/6] blk-cgroup: buffered write IO controller - bandwidth limit interface > > [PATCH 6/6] blk-cgroup: buffered write IO controller - debug trace > > > > How about a BOF on this topic during LSF/MM as there seems to be enough > interest? Sure. I'll talk briefly about the block IO cgroup in the writeback session. I'm open to more oriented technical discussions in some later time if necessary. Thanks, Fengguang -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
