On (01/28/19 10:16), Jan Kara wrote: > On Sun 27-01-19 16:36:34, [email protected] wrote: > > On Sun, 27 Jan 2019 17:00:27 +0100, Pavel Machek said: > > > > > I've noticed this as well on earlier kernels (next-20181224 to > > > > > 20190115) > > > > > Some more info: > > > > > 1) echo 3 > /proc/sys/vm/drop_caches unwedges kcompactd in 1-3 > > > > > seconds. > > > > This aspect is curious as it indicates that kcompactd could potentially > > > > be infinite looping but it's not something I've experienced myself. By > > > > any chance is there a preditable reproduction case for this? > > > > > > I seen it exactly once, so not sure how reproducible this is. x86-32 > > > machine, running chromium browser, so yes, there was some swapping > > > involved. > > > > I don't have a surefire replicator, but my laptop (x86_64, so it's not a > > 32-bit > > only issue) triggers it fairly often, up to multiple times a day. Doesn't > > seem to > > be just the Chrome browser that triggers it - usually I'm doing other stuff > > as > > well, like a compile or similar. The fact that 'drop_caches' clears it > > makes me > > wonder if we're hitting a corner case where cache data isn't being > > automatically > > cleared and clogging something up. > > So my buffer_migrate_page_norefs() is certainly buggy in its current > incarnation (as a result block device page cache is not migratable at all). > I've sent Andrew a patch over week ago but so far it got ignored. The patch > is attached, can you give it a try whether it changes something for you? > Thanks!
Hello Jan, Just for note, I'm seeing the same problems on my x86 box [1]. Don't have a reproducer for the issue yet, but will try to test your patch. Thanks. [1] https://lore.kernel.org/lkml/20190128085747.GA14454@jagdpanzerIV/T/#u -ss
