Re: Kernel SCM saga..

["H. Peter Anvin" <hpa@zytor.com>]

Daniel Phillips wrote:
> On Friday 08 April 2005 03:05, Rogan Dawes wrote:
>
> > Take a look at
> > http://www.linuxshowcase.org/2001/full_papers/ezolt/ezolt_html/
> >
> > Abstract
> >
> > GNU libc's default setting for malloc can cause a significant
> > performance penalty for applications that use it extensively, such as
> > Compaq's high performance extended math library, CXML.  The default
> > malloc tuning can cause a significant number of minor page faults, and
> > result in application performance of only half of the true potential.
>
>
> This does not smell like an n*2 suckage, more like n^something suckage.  
> Finding the elephant under the rug should not be hard.  Profile?

Lack of hysteresis can do that, with large swats of memory constantly 
being claimed and returned to the system.  One way to implement 
hysteresis would be based on a decaying peak-based threshold; 
unfortunately for optimal performance that requires the C runtime to 
have a notion of time, and in extreme cases even be able to do 
asynchronous deallocation, but in reality one can probably assume that 
the rate of malloc/free is roughly constant over time.

	-hpa
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