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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 <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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