Re: 2.2.0-pre[56] swap performance poor with > 1 thrashing task

Linus Torvalds
1999-01-09T06:46:00Z

Btw, if there are people there who actually like timing different things
(something I _hate_ doing - I lose interest if things become just a matter
of numbers rather than trying to get some algorithm right), then there's
one thing I'd love to hear about: the effect of trying to do some
access bit setting on buffer cache pages.

See my comments in linux/include/linux/fs.h, at around line 260 or so.
It's the "touch_buffer()" macro which is currently a no-op, and it is
entirely possible that it really should set the PG_referenced bit.

As a no-op, it can now randomly and unprectably result in even worthwhile
buffers just being thrown out - possibly quite soon after they've been
loaded in. I happen to believe that it doesn't actually matter (and I'm
not convinced that marking the pages referenced has no downsides), but I'm
too lazy to bother to test it.

Linus