On Fri, Oct 21, 2016 at 09:25:10AM +0200, Vlastimil Babka wrote: > On 10/21/2016 12:59 AM, Dave Chinner wrote: > >On Thu, Oct 20, 2016 at 03:33:58PM +0200, Michal Hocko wrote: > >>On Thu 20-10-16 14:11:49, Vlastimil Babka wrote: > >>[...] > >>> Hi, I'm wondering if people would find this useful. If you think it is, and > >>> to not make performance worse, I could also make sure in proper submission > >>> that values are not read via global_page_state() multiple times etc... > >> > >>I definitely find this information useful and hate to do the math all > >>the time but on the other hand this is quite fragile and I can imagine > >>we can easily forget to add something there and provide a misleading > >>information to the userspace. So I would be worried with a long term > >>maintainability of this. > > > >This will result in valid memory usage by subsystems like the XFS > >buffer cache being reported as "unaccounted". Given this cache > >(whose size is shrinker controlled) can grow to gigabytes in size > >under various metadata intensive workloads, there's every chance > >that such reporting will make users incorrectly think they have a > >massive memory leak.... > > Is the XFS buffer cache accounted (and visible) somewhere then? I'd > say getting such large consumers to become visible on the same level > as others would be another advantage... It's handles are visible via the xfs_buf slab cache. By the time you've got enough memory in the buffer cache for it to be noticed, the xfs_buf slab is near the top of the list in slabtop. Of course, because of the crazy way slub names caches, this can be impossible to find because there isn't a "xfs_buf" slab cache that shows up in slabtop. It'll end being called something like "mnt_cache".... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- 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>