On Thu 29-07-10 19:51:42, Wu Fengguang wrote: > Andrew, > > It's possible to transfer ASYNC vmscan writeback IOs to the flusher threads. > This simple patchset shows the basic idea. Since it's a big behavior change, > there are inevitably lots of details to sort out. I don't know where it will > go after tests and discussions, so the patches are intentionally kept simple. > > sync livelock avoidance (need more to be complete, but this is minimal required for the last two patches) > [PATCH 1/5] writeback: introduce wbc.for_sync to cover the two sync stages > [PATCH 2/5] writeback: stop periodic/background work on seeing sync works > [PATCH 3/5] writeback: prevent sync livelock with the sync_after timestamp Well, essentially any WB_SYNC_NONE writeback is still livelockable if you just grow a file constantly. So your changes are a step in the right direction but won't fix the issue completely. But what we could do to fix the issue completely would be to just set wbc->nr_to_write to LONG_MAX before writing inode for sync use my livelock avoidance using page-tagging for this case (it wouldn't have the possible performance issue because we are going to write all the inode anyway). I can write the patch but frankly there are so many patches floating around that I'm not sure what I should base it on... Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
