On Thu, Aug 16, 2012 at 10:28 PM, Glauber Costa <glommer@xxxxxxxxxxxxx> wrote: > On 08/17/2012 12:53 AM, Ying Han wrote: >> The same patch posted two years ago at: >> http://permalink.gmane.org/gmane.linux.kernel.mm/55467 >> >> No change since then and re-post it now mainly because it is part of the >> patchset I have internally. Also, the issue that the patch addresses would >> be more problematic after the patchset. >> >> Two changes included: >> 1. only remove inode with pages in its mapping when reclaim priority hits 0. >> >> It helps the situation when shrink_slab() is being too agressive, it ends up >> removing the inode as well as all the pages associated with the inode. >> Especially when single inode has lots of pages points to it. >> >> The problem was observed on a production workload we run, where it has small >> number of large files. Page reclaim won't blow away the inode which is pinned >> by dentry which in turn is pinned by open file descriptor. But if the >> application is openning and closing the fds, it has the chance to trigger >> the issue. The application will experience performance hit when that happens. >> >> After the whole patchset, the code will call the shrinker more often by adding >> shrink_slab() into target reclaim. So the performance hit will be more likely >> to be observed. >> >> 2. avoid wrapping up when scanning inode lru. >> >> The target_scan_count is calculated based on the userpage lru activity, >> which could be bigger than the inode lru size. avoid scanning the same >> inode twice by remembering the starting point for each scan. >> >> Signed-off-by: Ying Han <yinghan@xxxxxxxxxx> > > I don't doubt the problem, but having a field in sc that is used for > only one shrinker, and specifically to address a corner case, sounds > like a bit of a hack. Hmm, i don't see adding a extra field into shrink_control could be a big problem here. and I would argue it is a corner case as well :) This could happen anytime depending on the workload, and it could be even possible to have all the inode in that state. > > Wouldn't it be possible to make sure that such inodes are in the end of > the shrinkable list, so they are effectively left for last without > messing with priorities? You mean rotate them to the end of the list? Thought that is what the patch end up doing. --Ying -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>