Did you ever think CPU accounting might be slightly different?

Unless you know how to really profile the app I'd defer to the wisdom of
others.

On Fri, 2003-12-19 at 18:16, SN wrote:
> Okay, I want to summarize my experience with kernel 2.6 now.
> 
> I upgraded to the 2.6 final yesterday and ran some tests yesterday and all
> day today.
> First of all, kernel 2.6 worked fine, no crashes , all my drivers worked all
> my apps worked, all my hardware worked.
> 
> Test with overnet however revealed some issues, overnets CPU time usage is
> much higher with kernel 2.6.
> 
> The first test I ran was overnet with glibc without nptl, overnet used about
> twice as much cpu time as before with kernel 2.4.
> For the second test I installed linux-headers 2.6-beta11 and compiled  glibc
> with nptl (use flag nptl was set), the result stayed the same.
> 
> So overnet used about 15-20% cpu time with kernel 2.6 , with 2.4 it was
> around 5-10% .
> 
> To be able to compare the two results I ran the tests for hours and compared
> the cpu time whenever overnet build up aproximately the same number of tcp
> connections(measured with netstat) and the same number of openfiles(measured
> with lsof).
> Another effect:
> After compiling in nptl I noticed, that top gets confused by nptl the values
> it shows are not correct anymore. For example while compiling the
> accumulated cpu time is 90% but the compile process  cc1 shows that  it is
> using 2-5% cpu time and all other processes show about 0%, cc1 normally is
> around 90% while compiling, I upgraded procps to the latest release because
> top belongs to procps, but that didn't help it. So top is not working
> corectly with nptl.
> 
> 
> Although the system seems very responsive now I think something is wrong
> with 2.6
> I'm not really sure what causes this, it could be due to the new TCP Stack,
> a result of the new sheduling, or thread handling. Who knows???
> 
> I would love to see a discussion about that and maybe some other tests with
> other applications, for example a webserver or database server under high
> load.
> 
> GrÃÃe Stefan
> 
> 
> 
> 
> 
> 
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