Re: [gentoo-dev] Optimizing performance

[Patrick Lauer <patrick@gentoo.org>]

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On Thu, 2005-12-15 at 14:43 +0100, Francesco Riosa wrote:
> having more than one disk or a lot of memory add very interesting
> addition, read raid 0 (stripe) or tmpfs for working data that does'nt
> need a backup fex: $PORTIR, /var/tmp ...
tmpfs has miserable performance when larger than RAM iirc - you'd need >5G for openoffice :-)

> I've found that preemption with the new standard 250Hz of the kernel is
> suitable for mostly needs, however no server here has preemption enabled ;-)
My system still manages to run a DVD at a load of ~8, so from my point of view that is not a problem
(2Ghz Athlon ... one of the "faster" machines I'd say as many people
still use ~500Mhz)

What causes more problems are packages that become slow on update - e.g.
gtk+ 2.8 is _really_ slow (takes a few seconds to redraw apps that took
<1sec with 2.6 ... :-( )
> what is a normal workload ? Define it and creating tests should not be
> so difficult, then there are apps that can help to profiling, thinking
> at bootchart, sysproof, memproof, valgrind ... strace
I guess then you'd have to split into server / desktop / ...


> reiserfs is sustainable, at least for 99.999% of uses, last reiserfs bug
> on very high load (and with degraded raid5) is dated 4 years ago here.
> However upstream is going to the route of reiser4, much more complex,
> and much more unstable, latest problems where in 2.6.14, additionally no
> devs in gentoo are (will?) support it the patch for grub it's still not
> in place I think.
reiser4 is "new and untested", I'd keep away from it until it has shown its reliability.
Also in my (limited) testing it is relatively slow (about the same speed
as reiser3)
 
> > Are there any application-specific tweaks (e.g. "use the prefork MPM
> > with apache2")? What is known to break things, what has usually
> > beneficial behaviour? Are there any useful benchmarks that show the
> > performance difference between different settings?
> is'n there "ab" [1] for apache testing ?
Yes, but that's apache specific and is quite hard to use correctly.
(but very nice for slashdotting simulation ;-) )

Patrick
-- 
Stand still, and let the rest of the universe move

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