This sounds like the problem I was having where /tmp was on a physical
disk and not mounted on tmpfs. With out it your UML's memory file is
created on disk. This works fine since the cache is always hit, until
disk I/O pushes the memory image out of cache.
Check to make sure you have /tmp mounted on a tmpfs file system.
Chip Schweiss
-----Original Message-----
From: linux [mailto:linux@xxxxxxxxxxxx]
Sent: Tuesday, October 21, 2003 10:45 AM
To: user-mode-linux-user
Subject: [uml-user] Hangups with UML 2.4.22-5um on Heavy Disk Access
I have set up UML 2.4.22-5um on two machines with identical
software (Debian 3.0, kernel 2.4.22-ska3). I am using sparse files for
the
disk images used by the UML instances. UML boots and runs just fine, for
the most part.
When I am installing packages inside an UML, or copying large
amounts of data into the UML (from the network), the entire UML instance
has a tendency to lock up for a short amount of time. This also occurs
if
the host is busy with heavy disk access (resulting in any UML instance
that is trying to write at the same time, locking up). The UML instance
always recovers, and it primarily only occurs when the actual host disk
usage by the sparse file has to be increased.
I have seen some posts to this list that expanding the on disk
usage of a sparse file can be time consuming. But the strange part of
this
problem is that on one machine, these lockups are less than a second (a
few hundred milliseconds), and on the other machine they are several
seconds (10-40 seconds). The former machine is a P2-400 w/256MB RAM, and
30GB IDE HD. The latter machine is a Athlon 1.4GHz w/1GB RAM, and 3x36GB
Ultra160 RAID5 (software) SCSI array. So, yes, the far faster machine is
showing these lockups much worse than the slower machine. :(
This is not a show stopper for my use of UML, since most of the
time the disk space usage by a UML instance is steady state. Only when
more disk is needed, does it performance become "painful". I am curious
why the faster machine has more problems than the slower machine, any
one
have any ideas? Thanks.
PS. The faster machine is using high memory support in both the
host and UML kernel, but disabling it in both makes no difference in
behavior.
------------------------------------------------------------------------
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| "For to me to live is Christ, and to die is gain."
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| Ryan Kirkpatrick | Boulder, Colorado | http://www.rkirkpat.net/
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