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List:       linux-mm
Subject:    Re: Out of VM idea
From:       Rik van Riel <H.H.vanRiel () phys ! uu ! nl>
Date:       1998-04-30 20:57:02
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On 29 Apr 1998, Zlatko Calusic wrote:

> > You can tune the buffermem & pagecache amount of memory
> > in /proc/sys/vm/{buffermem,pagecache}.
> 
> Every time before he starts compiling, and then return to old values
> when he's finished?
> 
> IMNSHO, kernel should be autotuning.

How do you propose we should do this? The round-robin
deallocation and on-demand allocation of buffer/user
pages are somewhat auto-tuning.
Maybe we should age the page cache & buffermem pages
to achieve a more LRU-like discarding scheme (the
buffer pages are thrown out randomly at the moment).

> > But why your system has 4 MB of free memory I really
> > don't know...

> 	if (nr_free_pages > num_physpages >> 4)
> 		return nr+1;
> 
> With 64MB of memory, last 4MB are almost never used!!!

I believe George said something about my patch, with
which the number should be lower.
Anyway, the freepages number should be sysctl tunable,
together with kswapd agressiveness and clustering
size.

> MM in last kernels is not very good.

True, but maybe Linus will integrate my patch, which
makes the kernel behave somewhat more predictable, and
which has a builtin low/high watermark so thrashing is
reduced.

Rik.
+-------------------------------------------+--------------------------+
| Linux: - LinuxHQ MM-patches page          | Scouting       webmaster |
|        - kswapd ask-him & complain-to guy | Vries    cubscout leader |
|     http://www.phys.uu.nl/~riel/          | <H.H.vanRiel@phys.uu.nl> |
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