On Wed, May 18, 2011 at 10:47:18AM +0100, Mel Gorman wrote: > As we are aggressively shrinking slab, we can reach the stage where > we scan the requested number of objects and reclaim none of them > potentially setting zone->all_unreclaimable to 1 if a lot of scanning > has also taken place recently without pages being freed. Once this > happens, kswapd isn't even trying to reclaim pages and is instead stuck > in shrink_slab until a page is freed clearing zone->all_unreclaimable > and zone->pages-scanned. Isn't this completely broken then? We can have slabs with lots of objects but none are reclaimable - e.g. dirty inodes are not even on the inode LRU and require IO to get there, so repeatedly scanning the slab trying to free inodes is completely pointless. If the shrinkers are not freeing anything, then it should be backing off and giving thme some time to clean objects is a much more efficient use of CPU time than spinning madly. Indeed, if you back off, you can do another pass over the LRU and see if there are more pages that can be reclaimed, too, so you're not dependent on the shrinkers actually making progress to break the livelock.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
