Re: [PATCH] kswapd fully sysctl tunable

Linus Torvalds (
Sat, 2 May 1998 14:19:24 -0700 (PDT)

On Sat, 2 May 1998, MOLNAR Ingo wrote:
> > +dcache_agressive This option can be used when the dcache
> > + is taking up too much memory. This usually
> > + only happens on machines with less than 16
> > + megabytes of RAM. Increasing this value makes
> > + kswapd prune the dcache more agressively, but
> > + it makes name cacheing less effective, causing
> > + more disk reads and decreased performance.
> > + Use this when you need to, but use with care!
> not nitpicking, but i'm wondering wether this option just hides the real
> problem. Shouldnt the dcache notice such low-mem situations automagically?

I have something which should work. I think Rik has been hiding the
problem and I just noticed that I accepted into 99 a patch that definitely
should _not_ go in (the thing to change the "state" variable whether a
free operation works or not is wrong - we want to keep freeing from one
pool as long as it is "easy".

Rik, if you have problems with this under certain circumstances (like
swapping out too much even though there is plenty of buffers left), that
indicates that something is being too aggressive even though "i" (the
"aggressivemess factor") is set to a high value ("i = 6" means that it
shouldn't try all that hard, while "i = 0" means that we're really close
to meltdown and we should go crazy).


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