experiences beyond 4 GB RAM with 2.4.22

[Stephan von Krawczynski <skraw@ithnet.com>]

Hello,

lately I upgraded my testbox from 2 to 6 GB ram and found out some oddities I
would like to hear your opinions.
The box ran flawlessly and performant with 2 GB - was in fact a real joy.
After upgrading the ram and recompiling kernel 2.4.22 with support for 64 GB I
noticed:

1) nfs clients see timeouts again, like

Sep  9 03:37:35 clienta kernel: nfs: server 192.168.1.1 not responding, still
trying
Sep  9 03:37:35 clienta kernel: nfs: server 192.168.1.1 OK
Sep  9 03:37:35 clienta kernel: nfs: server 192.168.1.1 not responding, still
trying
Sep  9 03:37:35 clienta kernel: nfs: server 192.168.1.1 OK
Sep  9 03:41:13 clienta kernel: nfs: server 192.168.1.1 not responding, still
trying
Sep  9 03:41:13 clienta kernel: nfs: server 192.168.1.1 OK

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?

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.

I am really astonished about this. Can some kind soul give me hints or maybe
patches to try?

Regards,
Stephan