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

[Edward Shishkin]

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.

Edward.


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