Re: random minor benchmark: Re: Copy 20 tarfiles: ext2 vs (reiser4, unixfile) vs (reiser4,cryptcompress)

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On Thu, Jan 26 2006, Edward Shishkin wrote:
> Jens Axboe wrote:
> 
> >On Thu, Jan 26 2006, Edward Shishkin wrote:
> > 
> >
> >>Jens Axboe wrote:
> >>
> >>   
> >>
> >>>On Wed, Jan 25 2006, Hans Reiser wrote:
> >>>
> >>>
> >>>     
> >>>
> >>>>Notice how CPU speed (and number of cpus) completely determines
> >>>>compression performance.
> >>>>
> >>>>cryptcompress refers to the reiser4 compression plugin, (unix file)
> >>>>refers to the reiser4 non-compressing plugin.
> >>>>
> >>>>Edward Shishkin wrote:
> >>>>
> >>>> 
> >>>>
> >>>>       
> >>>>
> >>>>>Here are the tests that vs asked for:
> >>>>>Creation (dd) of 20 tarfiles (the original 200M file is in ramfs)
> >>>>>Kernel: 2.6.15-mm4 + current git snapshot of reiser4
> >>>>>
> >>>>>------------------------------------------
> >>>>>
> >>>>>Laputa workstation
> >>>>>Uni Intel Pentium 4 (2.26 GHz) 512M RAM
> >>>>>
> >>>>>ext2:
> >>>>>real 2m, 15s
> >>>>>sys 0m, 14s
> >>>>>
> >>>>>reiser4(unix file)
> >>>>>real 2m, 7s
> >>>>>sys  0m, 23s
> >>>>>
> >>>>>reiser4(cryptcompress, lzo1, 64K)
> >>>>>real 2m, 13s
> >>>>>sys 0m, 11s
> >>>>>   
> >>>>>
> >>>>>         
> >>>>>
> >>>Just curious - does your crypt plugin reside in user space?
> >>>
> >>>
> >>>
> >>>     
> >>>
> >>Nop.
> >>This is just wrappers for linux crypto api, zlib, etc..
> >>so user time is zero and not interesting.
> >>   
> >>
> >
> >Then why is the sys time lower than the "plain" writes on ext2 and
> >reiser4? Surely compressing isn't for free, yet the sys time is lower on
> >the compression write than the others.
> >
> > 
> >
> 
> I guess this is because real compression is going in background
> flush, not in sys_write->write_cryptcompress (which just copies
> user's data to page cache). So in this case we have something
> very similar to ext2. Reiser4 plain write (write_unix_file) is
> more complex, and currently we try to reduce its sys time.

So the systime quoted above is basically useless, it doesn't reflect the
real time spent in the kernel by far. I think you should note that when
you post these scores, otherwise you're really showing a skewed picture.

-- 
Jens Axboe

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