On Wed, 2008-08-20 at 20:48 +0900, Hirokazu Takahashi wrote: > Hi, > > > > Tsuruta-san, how about your bio-cgroup's tracking concerning this? > > > If we want to use your tracking functions for each threads seperately, > > > there seems to be a problem. > > > ===cf. mm_get_bio_cgroup()=================== > > > owner > > > mm_struct ----> task_struct ----> bio_cgroup > > > ============================================= > > > In my understanding, the mm_struct of a thread is same as its parent's. > > > So, even if we attach the TIDs of some threads to different cgroups the > > > tracking always returns the same bio_cgroup -- its parent's group. > > > Do you have some policy about in which case we can use your tracking? > > > > > It's will be resitriction when io-controller reuse information of the owner > > of memory. But if it's very clear who issues I/O (by tracking read/write > > syscall), we may have chance to record the issuer of I/O to page_cgroup > > struct. > > This might be slightly different topic though, > I've been thinking where we should add hooks to track I/O reqeust. > I think the following set of hooks is enough whether we are going to > support thread based cgroup or not. > > Hook-1: called when allocating a page, where the memory controller > already have a hoook. > Hook-2: called when making a page in page-cache dirty. > > For anonymous pages, Hook-1 is enough to track any type of I/O request. > For pages in page-cache, Hook-1 is also enough for read I/O because > the I/O is issued just once right after allocting the page. > For write I/O requests to pages in page-cache, Hook-1 will be okay > in most cases but sometimes process in another cgroup may write > the pages. In this case, Hook-2 is needed to keep accurate to track > I/O requests. This relative simplicity is what prompted me to say that we probably should try to disentangle the io tracking functionality from the memory controller a bit more (of course we still should reuse as much as we can from it). The rationale for this is that the existing I/O scheduler would benefit from proper io tracking capabilities too, so it'd be nice if we could have them even in non-cgroup-capable kernels. As an aside, when the IO context of a certain IO operation is known (synchronous IO comes to mind) I think it should be cashed in the resulting bio so that we can do without the expensive accesses to bio_cgroup once it enters the block layer. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
