Re: [PATCH 0/1] Possible bug in zram on ppc64le on vfat

[Martin Doucha]

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.

Note that I had to disable the other filesystems in the test because 
some of them kept failing with compression ratio <1.

--
Martin Doucha   mdoucha@xxxxxxx
QA Engineer for Software Maintenance
SUSE LINUX, s.r.o.
CORSO IIa
Krizikova 148/34
186 00 Prague 8
Czech Republic