On Fri, 2008-08-08 at 20:39 +0900, Hirokazu Takahashi wrote: > Hi, > > > > Would you like to split up IO into read and write IO. We know that read can be > > > very latency sensitive when compared to writes. Should we consider them > > > separately in the RFC? > > Oops, I somehow ended up leaving your first question unanswered. Sorry. > > > > I do not think we should consider them separately, as long as there is a > > proper IO tracking infrastructure in place. As you mentioned, reads can > > be very latecy sensitive, but the read case could be treated as an > > special case IO controller/IO tracking subsystem. There certainly are > > optimization opportunities. For example, in the synchronous I/O patch ww > > could mark bios with the iocontext of the current task, because it will > > happen to be originator of that IO. By effectively caching the ownership > > information in the bio we can avoid all the accesses to struct page, > > page_cgroup, etc, and reads would definitively benefit from that. > > FYI, we should also take special care of pages being reclaimed, the free > memory of the cgroup these pages belong to may be really low. > Dm-ioband is doing this. Thank you for the heads-up. - Fernando -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
