Re: zram: per-cpu compression streams

[Minchan Kim]

On Wed, Mar 30, 2016 at 05:34:19PM +0900, Sergey Senozhatsky wrote:
> Hello Minchan,
> sorry for long reply.
> 
> On (03/28/16 12:21), Minchan Kim wrote:
> [..]
> > group_reporting
> > buffer_compress_percentage=50
> > filename=/dev/zram0
> > loops=10
> 
> I used a bit different script. no `buffer_compress_percentage' option,
> because it provide "a mix of random data and zeroes"

Normally, zram's compression ratio is 3 or 2 so I used it.
Hmm, isn't it more real practice usecase?
If we don't use buffer_compress_percentage, what's the content in the buffer?

> 
> buffer_compress_percentage=int
>     If this is set, then fio will attempt to provide IO buffer content
>     (on WRITEs) that compress to the specified level. Fio does this by
>     providing a mix of random data and zeroes
> 
> and I also used scramble_buffers=0. but default scramble_buffers is
> true, so
> 
> scramble_buffers=bool
>     If refill_buffers is too costly and the target is using data
>     deduplication, then setting this option will slightly modify the IO
>     buffer contents to defeat normal de-dupe attempts. This is not
>     enough to defeat more clever block compression attempts, but it will
>     stop naive dedupe of blocks. Default: true.
> 
> hm, but I guess it's not enough; fio probably will have different
> data (well, only if we didn't ask it to zero-fill the buffers) for
> different tests, causing different zram->zsmalloc behaviour. need
> to check it.
> 
> 
> > Hmm, Could you retest to who how the benefit is big?
> 
> sure. the results are:
> 
> - seq-read
> - rand-read
> - seq-write
> - rand-write  (READ + WRITE)
> - mixed-seq
> - mixed-rand  (READ + WRITE)
> 
> TEST        4 streams     8 streams       per-cpu
> 
> #jobs1               	           	           
> READ:      2665.4MB/s	 2515.2MB/s	 2632.4MB/s
> READ:      2258.2MB/s	 2055.2MB/s	 2166.2MB/s
> WRITE:     933180KB/s	 894260KB/s	 898234KB/s
> WRITE:     765576KB/s	 728154KB/s	 746396KB/s
> READ:      563169KB/s	 541004KB/s	 551541KB/s
> WRITE:     562660KB/s	 540515KB/s	 551043KB/s
> READ:      493656KB/s	 477990KB/s	 488041KB/s
> WRITE:     493210KB/s	 477558KB/s	 487600KB/s
> #jobs2               	           	           
> READ:      5116.7MB/s	 4607.1MB/s	 4401.5MB/s
> READ:      4401.5MB/s	 3993.6MB/s	 3831.6MB/s
> WRITE:     1539.9MB/s	 1425.5MB/s	 1600.0MB/s
> WRITE:     1311.1MB/s	 1228.7MB/s	 1380.6MB/s
> READ:      1001.8MB/s	 960799KB/s	 989.63MB/s
> WRITE:     998.31MB/s	 957540KB/s	 986.26MB/s
> READ:      921439KB/s	 860387KB/s	 899720KB/s
> WRITE:     918314KB/s	 857469KB/s	 896668KB/s
> #jobs3               	           	           
> READ:      6670.9MB/s	 6469.9MB/s	 6548.8MB/s
> READ:      5743.4MB/s	 5507.8MB/s	 5608.4MB/s
> WRITE:     1923.8MB/s	 1885.9MB/s	 2191.9MB/s
> WRITE:     1622.4MB/s	 1605.4MB/s	 1842.2MB/s
> READ:      1277.3MB/s	 1295.8MB/s	 1395.2MB/s
> WRITE:     1276.9MB/s	 1295.4MB/s	 1394.7MB/s
> READ:      1152.6MB/s	 1137.1MB/s	 1216.6MB/s
> WRITE:     1152.2MB/s	 1137.6MB/s	 1216.2MB/s
> #jobs4               	           	           
> READ:      8720.4MB/s	 7301.7MB/s	 7896.2MB/s
> READ:      7510.3MB/s	 6690.1MB/s	 6456.2MB/s
> WRITE:     2211.6MB/s	 1930.8MB/s	 2713.9MB/s
> WRITE:     2002.2MB/s	 1629.8MB/s	 2227.7MB/s

Your case is 40% win. It's huge, Nice!
I tested with your guide line(i.e., no buffer_compress_percentage,
scramble_buffers=0) but still 10% enhance in my machine.
Hmm,,,

How about if you test my fio job.file in your machine?
Still, it's 40% win?

Also, I want to test again in your exactly same configuration.
Could you tell me zram environment(ie, disksize, compression
algorithm) and share me your job.file of fio?


Thanks.