On Wednesday, March 2, 2016, Vivek Goyal <vgo...@redhat.com> wrote: > On Wed, Mar 02, 2016 at 08:03:10PM +0200, Nikolay Borisov wrote: > > Thanks for the patch I will likely have time to test this sometime next > week. > > But just to be sure - the expected behavior would be that processes > > writing to dm-based devices would experience the fair-shair > > scheduling of CFQ (provided that the physical devices that back those > > DM devices use CFQ), correct? > > Nikolay, > > I am not sure how well it will work with CFQ of underlying device. It will > get cgroup information right for buffered writes. But cgroup information
Right, what's your definition of buffered writes? My mental model is that when a process submits a write request to a dm device , the bio is going to be put on a devi e workqueue which would then be serviced by a background worker thread and later the submitter notified. Do you refer to this whole gamut of operations as buffered writes? for reads and direct writes will come from submitter's context and if dm > layer gets in between, then many a times submitter might be a worker > thread and IO will be attributed to that worker's cgroup (root cgroup). Be that as it may, proivded that the worker thread is in the 'correct' cgroup, then the appropriate babdwidth policies should apply, no? > > Give it a try anyway. Most certainly I will :) > > Thanks > Vivek >
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