Re: [PATCH] kswapd performance fix

[Rik van Riel <riel@nl.linux.org>]

On Fri, 25 Feb 2000, Stephen C. Tweedie wrote:
> On Fri, 25 Feb 2000 00:30:59 +0100 (CET), Rik van Riel
> <riel@nl.linux.org> said:
> 
> > The patch should apply to any 2.2 or 2.3 kernel, but for
> > 2.3 it'll have the interesting side effect of nullifying
> > the (minimal) page aging that's going on there.
> 
> Have you actually tested the impact of this under a variety of
> load conditions?  In the past we have seen such apparently trivial
> changes completely break the VM balance under certain loads.

The PG_referenced bit isn't used for anything except for
NRU/LRU page reclaiming in shrink_mmap().

However, shrink_mmap() will skip over any pages that are
still mapped by processes _and_ when we unmap the page
from the (next to) last user we set the PG_referenced bit.

The PG_referenced bit is also not used at all by shrink_mmap(),
unless (page->count == 1); shm_swap() doesn't use the referenced
bit at all.

regards,

Rik
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