> On 11. 11. 22 1:48, Sergey Senozhatsky wrote: > > On (22/11/10 15:29), Martin Doucha wrote: > > > I've tried to debug the issue and collected some interesting data (all > > > values come from zram device with 25M size limit and zstd compression > > > algorithm): > > > - mm_stat values are correct after mkfs.vfat: > > > 65536 220 65536 26214400 65536 0 0 0 > > > - mm_stat values stay correct after mount: > > > 65536 220 65536 26214400 65536 0 0 0 > > > - the bug is triggered by filling the filesystem to capacity (using dd): > > > 4194304 0 0 26214400 327680 64 0 0 > > Can you try using /dev/urandom for dd, not /dev/zero? > > Do you still see zeroes in sysfs output or some random values? > After 50 test runs on a kernel where the issue is confirmed, I could not > reproduce the failure while filling the device from /dev/urandom instead of > /dev/zero. The test reported compression ratio around 1.8-2.5 which means > the memory usage reported by mm_stat was 10-13MB. Martin, thanks a lot for reruning tests. I wonder problems on /dev/zero is a kernel bug or just problem which should be workarounded. > Note that I had to disable the other filesystems in the test because some of > them kept failing with compression ratio <1. Yes, I noted that as well at least on exfat and btrfs (if I remember correctly). It wouldn't be a problem to just use it for vfat if we agreed test should be modified. Kind regards, Petr
