Date: Fri, 12 Sep 2003 08:54:35 +0200
From: Stephan von Krawczynski <skraw@ithnet.com>
To: Neil Brown <neilb@cse.unsw.edu.au>
Cc: linux-kernel@vger.kernel.org
Subject: Re: experiences beyond 4 GB RAM with 2.4.22
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On Fri, 12 Sep 2003 12:46:46 +1000
Neil Brown <neilb@cse.unsw.edu.au> wrote:

> > Both are 2.4.22. 192.168.1.1 is the testbox. I saw those with 2GB, but
> > could fix it through more nfs-daemons and
> > 
> >         echo 2097152 >/proc/sys/net/core/rmem_max
> >         echo 2097152 >/proc/sys/net/core/wmem_max
> > 
> > Are these values too small for 6 GB?
> 
> No.  The values are proportional to the number of server threads, not
> the amount of RAM... and they should be un-necessary after 2.4.20
> anyway as nfsd in the kernel makes the appropriate settings.

Oh. That's interesting. Then everything should be the same if I deleted
those...

> > 2) Box is very slow, kswapd looks very active during tar of a local
> > harddisk. Interactivity is really bad. Seems vm has a high time looking for
> > free or usable pages. Compared to 2 GB the behaviour is unbelievably bad.
> > 
> > 3) Network performance has a remarkable dropdown during above tar. In fact
> > doing simple pings every few minutes shows that quite a lot of them are
> > simply dropped, never make it over the ethernet.
> 
> My only guess is that it is doing a lot of copying into low memory
> because your devices can only DMA into/outof low memory.

I forgot to mention: Both network card and controller are 64 bit cards.
Network card is (vendor 3com):
Ethernet controller: Broadcom Corporation NetXtreme BCM5701 Gigabit Ethernet
(rev 15) (tg3-driver)
Controller is:
RAID bus controller: 3ware Inc 3ware 7000-series ATA-RAID (rev 01)
I have "CONFIG_HIGHIO=y"

> Have you tried 2.6 ??

No, not yet. I have not dared :-)

> How about CONFIG_HIGHMEM4G ?
> It won't use all the RAM, but it would be interesting if it were
> faster.

I already thought about that and tried. In fact it is as fast and fine as 2 GB
setup. It runs really smooth. 
The really simple test for the problem is running "updatedb" (find over the
whole filesystem). The box comes to a crawl while this is running, network is
absolutely bad, interactivity is rather dead, very often not even a ssh login
works.

Regards,
Stephan
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