On Wed, 22 Jul 2009 18:40:55 +0900 (JST) Ryo Tsuruta <ryov@xxxxxxxxxxxxx> wrote: > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > On Tue, 21 Jul 2009 23:23:16 +0900 (JST) > > Ryo Tsuruta <ryov@xxxxxxxxxxxxx> wrote: > > > > > This patch contains several hooks that let the blkio-cgroup framework to know > > > which blkio-cgroup is the owner of a page before starting I/O against the page. > > > > > @@ -464,6 +465,7 @@ int add_to_page_cache_locked(struct page > > > gfp_mask & GFP_RECLAIM_MASK); > > > if (error) > > > goto out; > > > + blkio_cgroup_set_owner(page, current->mm); > > > > > > > This part is doubtful...Is this necessary ? > > I recommend you that the caller should attach owner by itself. > > I think that it is reasonable to add the hook right here rather than > to add many hooks to a variety of places. > Why ? at writing, it's will be overwriten soon, IIUC. Then, this information is misleading. plz add a hook like this when it means something. In this case, read/write callers. IMO, you just increase patch's readbility but decrease easiness of maintaince. > > IMHO, later io for swap-out is caused by the caller of swapout, not page's > > owner. plz charge to them or, > > - add special BLOCK CGROUP ID for the kernel's swap out. > > I think that it is not too bad to charge the owner of a page for > swap-out. From another perspective, it can be considered that swap-out > is caused by a process which uses a large amount of memory. > No. swap-out is caused by a thread who requests memory even while memory is in short. IMHO, I/O by memory reqraim should work in priority of memory requester. Consider following situation. - A process "A" has big memory. When several threads requests memory, all of them are caught by a blockio cgroup of "A". - A process "B" has read big file caches. When several threads requests memory, all of them are caught by a blockio cgroup of "B". If "A" and "B" 's threshold is small, you'll see big slow down. But it's not _planned_ behavior in many cases. If you charges agaisnt memory owner, the admin has to set _big_ priority of I/O controller to "A" and "B" if it uses much memory. I think the admin can't design his system. It's nonsense to say "plz set I/O limit propotional to memory usage of your apps even if it never do I/O in usual." If this blockio cgroup is introduced, people will see *unexpected* very terrible slow down and the user will see heartbeat warnings/failover by cluster management software. Please do I/O at the priority of memory reclaiming requester. Thanks, -Kame -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
