It sounds like you have the same problem I'm having on my dual Xeon 2.8
Ghz with 8GB ram.
It has something to do with using highmem (I'm using 512mb in a UML),
and when you turn the memory down to something around 128-256mb, it goes
alot faster.
I tested it out with 1024mb, and it was so slow that the UML session
couldn't keep up with itself and was at a UML load average of 22+.
(This is with the TMPDIR set to /dev/shm)
I don't know if there's a fix for this, but it's what is happening.
--Dan
Martinez Gonzalez, Francisco wrote:
I have the skas patch in the host, and I export the TMPDIR as example below,
but I have the same result: UML is very slow, booting (2 minutes) and after
too.
The host machine is an 4 processor P4 Xeon 2G (multithread) with 4GB ram.
What's happening?
Thanks Thanks
-----Mensaje original-----
De: BlaisorBlade [mailto:blaisorblade_spam@xxxxxxxx]
Enviado el: jueves, 05 de febrero de 2004 19:53
Para: user-mode-linux-user@xxxxxxxxxxxxxxxxxxxxx
CC: Martinez Gonzalez, Francisco
Asunto: Re: [uml-user] UML too slow.
Alle 12:37, giovedì 5 febbraio 2004, Martinez Gonzalez, Francisco ha
scritto:
Hello,
The case is that we are testing a machine with 8 processors and 16GB of
ram, in which we would like to raise several images UML (6 or 8), and when
we raised an image without passing the parameter "mem =" it goes very
speed, but at the moment in which we indicated the parameter "mem=256M" or
more, the starting of that UML is slowest, reason why we did not raise the
more when seeing the slowness of this one. According to I have been
reading, UML doesn't take physical memory of host, if that creates a file
in filesystem of host with the size indicated in the parameter "mem =".
Yes, this is true. That file is inside /tmp normally (i.e. on your disk) and
is deleted (so only ls /proc/<umlpid>/fd or lsof can show it). But if you
do:
export TMPDIR=/dev/shm
<start UML>
unset TMPDIR
then the file will go onto /dev/shm, which is a RAM-based filesystem (i.e.
the
file, actually, is on RAM). This will make it a lot faster. Also, remember
using the skas patch on the host for speed.
Bye
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