On Wed, 16 Jun 2021 at 14:59, Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Wed, Jun 16, 2021 at 02:31:32PM +0200, Miklos Szeredi wrote: > > On Mon, 14 Jun 2021 at 11:56, Thomas Lindroth <thomas.lindroth@xxxxxxxxx> wrote: > > > > > > Hi. I recently upgraded to kernel series 5.10 from 4.19 and I now get warnings like > > > this in dmesg: > > > > > > page:00000000e966ec4e refcount:1 mapcount:0 mapping:0000000000000000 index:0xd3414 pfn:0x14914a > > > flags: 0x8000000000000077(locked|referenced|uptodate|lru|active|workingset) > > > raw: 8000000000000077 ffffdc7f4d312b48 ffffdc7f452452c8 0000000000000000 > > > raw: 00000000000d3414 0000000000000000 00000001ffffffff ffff8fd080123000 > > > page dumped because: fuse: trying to steal weird page > > > > > > The warning in fuse_check_page() doesn't check for PG_workingset which seems to be what > > > trips the warning. I'm not entirely sure this is a bogus warning but there used to be > > > similar bogus warnings caused by a missing PG_waiters check. The PG_workingset > > > page flag was introduced in 4.20 which explains why I get the warning now. > > > > > > I only get the new warning if I do writes to a fuse fs (mergerfs) and at the same > > > time put the system under memory pressure by running many qemu VMs. > > > > AFAICT fuse is trying to steal a pagecache page from a pipe buffer > > created by splice(2). The page looks okay, but I have no idea what > > PG_workingset means in this context. > > > > Matthew, can you please help? > > PG_workingset was introduced by Johannes: > > mm: workingset: tell cache transitions from workingset thrashing > > Refaults happen during transitions between workingsets as well as in-place > thrashing. Knowing the difference between the two has a range of > applications, including measuring the impact of memory shortage on the > system performance, as well as the ability to smarter balance pressure > between the filesystem cache and the swap-backed workingset. > > During workingset transitions, inactive cache refaults and pushes out > established active cache. When that active cache isn't stale, however, > and also ends up refaulting, that's bonafide thrashing. > > Introduce a new page flag that tells on eviction whether the page has been > active or not in its lifetime. This bit is then stored in the shadow > entry, to classify refaults as transitioning or thrashing. > > so I think it's fine for you to ignore when stealing a page. I have problem understanding what a workingset is. Is it related to swap? If so, how can such a page be part of a file mapping? Thanks, Miklos
