On Thu, 24 Mar 2016, Kirill A. Shutemov wrote: > On Wed, Mar 23, 2016 at 01:09:05PM -0700, Hugh Dickins wrote: > > The small files thing formed my first impression. My second > > impression was similar, when I tried mmap(NULL, size_of_RAM, > > PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_SHARED, -1, 0) and > > cycled around the arena touching all the pages (which of > > course has to push a little into swap): that soon OOMed. > > > > But there I think you probably just have some minor bug to be fixed: > > I spent a little while trying to debug it, but then decided I'd > > better get back to writing to you. I didn't really understand what > > I was seeing, but when I hacked some stats into shrink_page_list(), > > converting !is_page_cache_freeable(page) to page_cache_references(page) > > to return the difference instead of the bool, a large proportion of > > huge tmpfs pages seemed to have count 1 too high to be freeable at > > that point (and one huge tmpfs page had a count of 3477). > > I'll reply to your other points later, but first I wanted to address this > obvious bug. Thanks. That works better, but is not yet right: memory isn't freed as it should be, so when I exit then try to run a second time, the mmap() just gets ENOMEM (with /proc/sys/vm/overcommit_memory 0): MemFree is low. No rush to fix, I've other stuff to do. I don't get as far as that on the laptop, since the first run is OOM killed while swapping; but I can't vouch for the OOM-kill-correctness of the base tree I'm using, and this laptop has a history of OOMing rather too easily if all's not right. Hugh -- 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>