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SubjectRe: 2.6.0 performance problems
Thomas Molina <tmolina@cablespeed.com> wrote:
>
> On Tue, 30 Dec 2003, Linus Torvalds wrote:
> > Ok. This looks much closer to the 2.4.x numbers you reported:
> >
> > real 13m50.198s
> > user 0m33.780s
> > sys 0m15.390s
> >
> > so I assume that we can consider this problem largely solved? There's
> > still some difference, that could be due to just VM tuning..
> >
> > I suspect that what happened is:
> > - slab debugging adds a heavy CPU _and_ it also makes all the slab caches
> > much less dense.
> > - as a result, you see much higher system times, and you also end up
> > needing much more memory for things like the dentry cache, so your
> > memory-starved machine ended up swapping a lot more too.
>
> So you are telling me that I am paying the price for running development
> kernels and enabling all the debugging.

CONFIG_DEBUG_PAGEALLOC really does hurt on small machines. Mainly because
it rounds the size of all slab object which are >= 128 bytes up to a full
4k. So things like inodes and dentries take vastly more memory.

The other debug options are less costly.

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