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SubjectRe: experiences beyond 4 GB RAM with 2.4.22
On Fri, 12 Sep 2003 12:46:46 +1000
Neil Brown <> wrote:

> > Both are 2.4.22. 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

> > 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)

> 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

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