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[v2,0/1] Fix compression ratio calculation in zram01

Message ID 20191105090339.6522-1-mdoucha@suse.cz
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Series Fix compression ratio calculation in zram01 | expand

Message

Martin Doucha Nov. 5, 2019, 9:03 a.m. UTC 
Changes from v1:
- TINFO about amount of data written to zram device changed to TPASS

Shortened patch description from v1:
The compression ratio check in zram01.sh is completely broken. Here's a patch
to calculate the compression ratio correctly using sysfs memory usage
statistics for each zram device. I currently calculate it as
$bytes_written / $mm_stat_compr_data_size.

One question for debate is whether I should use a different formula:
- $bytes_written / $mm_stat_mem_used_total
  (mem_used_total includes internal zram memory management overhead)
- $mm_stat_orig_data_size / $mm_stat_compr_data_size
  (zram01.sh fills the zram device with binary zeroes so the data will be
  compacted even before compression; orig_data_size << bytes_written)
- $mm_stat_orig_data_size / $mm_stat_mem_used_total)
  (this could easily produce ratio <100% due to page compacting)
See https://www.kernel.org/doc/Documentation/blockdev/zram.txt

Martin Doucha (1):
  Fix compression ratio calculation in zram01

 .../kernel/device-drivers/zram/zram01.sh      | 38 +++++++++----------
 1 file changed, 17 insertions(+), 21 deletions(-)