KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > 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. Even though the owner is overwritten soon at writing, I'm not sure why inserting the hook here causes the misleading. I think that it is easy to understand when and where the owner is set by blkio-cgroup, and it does not decrease maintainability, rather than put many hooks to each caller. > > > 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. dm-ioband gives high priority to I/O for swap-out by checking whether PG_swapcache flag is set on the I/O page, regardless of the assigned I/O bandwidth, and the bandwidth consumed for swap-out is charged to the owner of the pages as a debt. How about this approach? Thanks, Ryo Tsuruta > > > Thanks, > -Kame > > > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxxxxxxxx > http://lists.xensource.com/xen-devel -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
