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To: Linus Torvalds <torvalds@transmeta.com>
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Subject: Re: xmm2 - monitor Linux MM active/inactive lists graphically
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Reply-To: zlatko.calusic@iskon.hr
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From: Zlatko Calusic <zlatko.calusic@iskon.hr>
Date: 25 Oct 2001 11:07:05 +0200
In-Reply-To: <Pine.LNX.4.33.0110242117150.9147-100000@penguin.transmeta.com> (Linus Torvalds's message of "Wed, 24 Oct 2001 21:19:55 -0700 (PDT)")
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Linus Torvalds <torvalds@transmeta.com> writes:

> On 25 Oct 2001, Zlatko Calusic wrote:
> >
> > Sure. Output of 'vmstat 1' follows:
> >
> >  1  0  0      0 254552   5120 183476   0   0    12    24  178   438 2  37  60
> >  0  1  0      0 137296   5232 297760   0   0     4  5284  195   440 3  43  54
> >  1  0  0      0 126520   5244 308260   0   0     0 10588  215   230 0   3  96
> >  0  2  0      0 117488   5252 317064   0   0     0  8796  176   139 1   3  96
> >  0  2  0      0 107556   5264 326744   0   0     0  9704  174    78 0   3  97
> 
> This does not look like a VM issue at all - at this point you're already
> getting only 10MB/s, yet the VM isn't even involved (there's definitely no
> VM pressure here).

That's true, I'll admit. Anyway, -ac kernels don't have the problem,
and I was misleaded by the fact that only VM implementation differs in
those two branches (at least I think so).

> 
> > Notice how there's planty of RAM. I'm writing sequentially to a file
> > on the ext2 filesystem. The disk I'm writing on is a 7200rpm IDE,
> > capable of ~ 22 MB/s and I'm still getting only ~ 9 MB/s. Weird!
> 
> Are you sure you haven't lost some DMA setting or something?
> 

No. Setup is fine. I wouldn't make such a mistake. :)
If the disk were in some PIO mode, CPU usage would be much higher, but
it isn't.

This all definitely looks like a problem either in the bdflush daemon,
or request queue/elevator, but unfortunately I don't have enough
knowledge of that areas to pinpoint it more precisely.
-- 
Zlatko
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