Performance tuning the Fedora Desktop

[Warren Togami]

Marius Andreiana wrote:
> On Thu, 2004-05-06 at 00:11, Will Cohen wrote:
> 
>>What specific performance problems have people observed so far in the
>>desktop?
> 
> when HDD is used by an application (copying a large file, updatedb...),
> all the applications respond slow. The preemptible kernel patch should
> solve this, but it's not enabled in FC2.
> 

Paraphrased from what Arjan van de Ven told me regarding kernel preempt.

Arjan said, "preempt doesn't help for the desktop (1ms to 0.8ms latency 
you don't notice *at all*) but that 4K stacks does make a big dent"

Warren said, "and overall runtime would be slower with preempt because 
the on-CPU cache is blown away more often"

Arjan said, "and it generates worse IO patterns -> slower disk io"

both aren't good for performance; worse disk IO means actually longer 
feeled latency

but really, humans don't notice latency < 10ms or so.

so anything below that is just fudzing with noise

however disk IO and things like the VM before 4K stacks can cause delays 
(not latencys) far longer than that

Warren Togami
wtogami at redhat.com