Fernando Luis Vázquez Cao wrote: > 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. > Hook 2 referred to in the mail above exist today in the form of task IO accounting. > 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. Will this give you everything you need for accounting and control (from the block layer?) -- Balbir _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
