Key for high CPU usage

[Leen Besselink]

Leen Besselink wrote:
> Daniel.Li wrote:
>> Dear List,
>>
>> I'm trying to take a closer look at rsync code, and found when we run
>> daemon, it will take a lot of CPU (400Mhz). So I'm interested in Which
>> part of rsync code on ver 3.0.5 consuming CPU a lot?
>>
>> Can anyone here help to lighten me up? So I can try to improve the
>> performance or low the CPU usage.
>>
>>
>> I suspect that there are a few factors, which might related with CPU
>> usage: rolling checksum/Disk IO(a slide window has been implemented),
>> read or write?
>>
>>
>> Hope I can find some info here! Thanks in advance! 
>>
>>
> 
> Hi Daniel,
> 
> Not sure how much you know about how rsync works, but maybe you first want
> to know how the algoritm works ? I'm fairly sure it's a large part of the
> CPU-usage:
> 
> http://www.samba.org/rsync/tech_report/
> 
> But I personally enjoyed the talk talk Andrew Tridgell did at OLS in 2000
> more, here is a transcript:
> 
> http://olstrans.sourceforge.net/release/OLS2000-rsync/OLS2000-rsync.html
> 
> Here are the slides of the talk:
> 
> ftp://ftp.samba.org/pub/tridge/talks/rsync_ols.tgz
> 
> I wouldn't be surprised if you were able to find the mp3 online somehere
> with the filename:
> 
> 2000-07-21_15-02-49_C_64.mp3
> 
> 

I was checking the talk and did find this bit:

"in fact the bottleneck, when people use the -z option, 90% of the CPU is
in gzip, you know, the zlib library."

So if you enabled compression, then you probably know where your CPU-time went.