On Tue, Sep 01, 2015 at 08:17:43AM +1000, Dave Chinner wrote: > The patch changes the bio allocation patterns - it allocates them on > the fly and holds them, so we could potentially exhaust the bio > mempool with this submission technique. I've spend time to look over the patch again, and still don't see a change. Both in the old and new code we walk over the ioends and build bios on the fly in xfs_submit_ioend(), which is always called near then end of the writeback code; at the end of xfs_vm_writepage in the old version, and from the end of xfs_vm_writepage/xfs_vm_writepages through xfs_writepage_submit in the new code (not taking the error case into account, which probably should moe there, too). The only big difference is.. > The ioend allocation pattern > is different, too, because we only used to have 1 per buffer on a > writepage call and the last one was used for the write clustering. .. that we now build up way bigger ioend chains. So back to Brians concern: we can now have fairly large piles of ioends built up while potentially getting scheduled out, and this does look like a potential real issue to me. I wonder if we should (ab-)use the blk_plug_cb infrastructure so that we can flush the pending ioends out on a context switch? _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
