On Wed, May 27, 2009 at 03:56:31PM +0900, Ryo Tsuruta wrote: > > I think that only putting the hook in try_to_unmap() doesn't work > > correctly, because IOs will be charged to reclaiming processes or > > kswapd. These IOs should be charged to processes which cause memory > > pressure. > > Consider the following case: > > (1) There are two processes Proc-A and Proc-B. > (2) Proc-A maps a large file into many pages by mmap() and writes > many data to the file. > (3) After (2), Proc-B try to get a page, but there are no available > pages because Proc-A has used them. > (4) kernel starts to reclaim pages, call try_to_unmap() to unmap > a page which is owned by Proc-A, then blkio_cgroup_set_owner() > sets Proc-B's ID on the page because the task's context is Proc-B. > (5) After (4), kernel writes the page out to a disk. This IO is > charged to Proc-B. > > In the above case, I think that the IO should be charged to a Proc-A, > because the IO is caused by Proc-A's memory pressure. > I think we should consider in the case without memory and swap > isolation. mmmh.. even if they're strictly related I think we're mixing two different problems in this way: memory pressure control and IO control. It seems you're proposing something like the badness() for OOM conditions to charge swap IO depending on how bad is a cgroup in terms of memory consumption. I don't think this is the right way to proceed, also because we already have the memory and swap control. -Andrea -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
