Re: Low latency for recent kernels

[Andrew Morton]

Mauricio Nuņez wrote:
> 
> Hi,
> 
> I'm sending some feedback !
> :-)

Is good.  Thanks.

> I'm trying this patch... (in 2.4.18-pre6)
> I'm feeling a improved performance ,as a desktop user.
> I'm working with KDE2, Netbeans and VMWare.
> Pentium III 666Mhz , 192M Ram, 10GB HD.

I'm a little surprised that desktop users do notice significant
benefits with all the latency/preempt patches.  If you actually
instrument the kernel's behaviour, the stalls are in fact
quite small and infrequent.  See the histograms in

 http://www.uwsg.iu.edu/hypermail/linux/kernel/0201.0/1624.html

Probably, poor interactivity on the desktop is more due to
waiting on disk reads - a combination of bad read latency
in the presence of write traffic and unfortunate page replacement
decisions.

Try http://www.zipworld.com.au/~akpm/linux/2.4/2.4.18-pre6/read-latency2.patch

> What are the tools to check this better performance?
> Or my impression is sufficient ?

The simplest tool to use is Mark Hahn's `realfeel' app.  See
http://www.zip.com.au/~akpm/linux/amlat.tar.gz

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