Re: [VM PATCH] Faster reclamation of dirty pages and unused inode/dcache entries in 2.4.22
From: Antonio Vargas
Date: Sat Aug 30 2003 - 02:34:05 EST
On Fri, Aug 29, 2003 at 01:20:01PM -0700, Shantanu Goel wrote:
> Thanks for the pointer to the benchmarks.
> The patch I posted only helps the mmap case so it
> won't help (or hurt hopefully ;-) any program that
> primarily does read/write instead of mmap. The
> extreme case where I observed this was a perl script
> that created a gigantic hash and tried to populate it.
I've experienced this workload and it's easily reproducible:
get the lxr tools and try to build the indexes.
> The perl in question uses mmap for malloc. The
> difference in execution time between stock 2.4.22 and
> one with the patch was insignificant because it is
> primarily I/O bound, however the other apps I was
> running, Mozilla and several xterm's, were paged out
> much less frequently in the latter case. The machine
> has 256MB of memory and perl grew to about 1 GB.
> I have written another patch that more aggresively
> tries to free pages with dirty buffers which should
> help with the buffer I/O case. It essentially changes
> try_to_free_buffers() so it immediately starts and
> waits for I/O to complete if the gfp_mask allows it.
> It does not do any clustering so its performance is
> questionable at the moment.
> --- Andrea Arcangeli <andrea@xxxxxxx> wrote:
> > On Fri, Aug 29, 2003 at 12:46:36PM -0700, Shantanu
> > Goel wrote:
> > > Andrea,
> > >
> > > I'll test and submit a patch against -aa. Also,
> > is
> > > there a common benchmark that you use to test for
> > > regression?
> > bonnie,tiobench,dbench would be a very good start
> > for the basics (note:
> > dbench can be misleading, but at the same fariness
> > levels, it's
> > interesting too, it's just that dbench doesn't
> > measure the fariness
> > level itself [like tiobench started doing relatively
> > recently]).
> > (I'm assuming the patch makes difference not only
> > for mmapped dirty
> > pages, in such case the above would be non
> > interesting)
> > thanks,
> > Andrea
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1. Dado un programa, siempre tiene al menos un fallo.
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3. Por induccion, todos los programas se pueden
reducir a una linea que no funciona.
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