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

[Edward Shishkin <edward@namesys.com>]

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.