Re: [PATCH] Optimize out pte_chain take three

Rik van Riel
2002-07-11T20:05:46Z

On Thu, 11 Jul 2002, Andrew Morton wrote:

> Rik thought these are pagecache and swap thrashers, but that's not
> the intent. Think of the file as program text and the malloced
> memory as, well, malloced memory.
>
> The problem is the access pattern. It shouldn't be random-uniform.
> But what should it be? random-gaussian?

> Does this not capture what the VM is supposed to do?

Indeed. This sounds like a much much better test.

> useful pagecache and swapping everything out. Our kernels have
> O_STREAMING because of this. It simply removes as much pagecache
> as it can, each time ->nrpages reaches 256. It's rather effective.

Now why does that remind me of drop-behind ? ;)

> I installed 2.5.25+rmap on my desktop yesterday. Come in this morning
> to discover half of memory is inodes, quarter of memory is dentries and
> I'm 40 megs into swap. Sigh.

As requested by Linus, this patch only has the mechanism
and none of the balancing changes.

I suspect Ed Tomlinson's patch will fix this issue.

> The `working set simulator' could provide the memory hog function.
> The victim application perhaps doesn't need to be anything as
> fancy on day one. Maybe just a kernel compile or such?

Or maybe the interactive performance measurement thing by
Bob Matthews ?

http://people.redhat.com/bmatthews/irman/ (IIRC)

> I'll do the working set simulator. That'll give you guys something
> to crunch on. Is gaussian reasonable?

Sounds ok to me.

kind regards,

Rik
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