blamere at diversa.com
Wed Dec 18 07:26:04 PST 2002
Problem is that its not a matter of whether the memory is really being used.
It's a matter of what is occurring to file caching. I don't care at all
what free says, other than the fact that I wish I knew bdflush better, or
Ths important factor is that this behavior did not occur until a month ago,
nothing seemingly important changed around that time, and the only way to
fix it is to reboot the cluster. Once rebooted, they perform literally 100
times better. If getting 100 times better performance when you reboot after
a week's time sounds normal to this list, then I guess I'll join another :/
For the life of me, I can't tell where else to look. I've got stock
(default) settings for the kernel's use of memory. I've dug around for a
while now, unable to make heads or tails of anything. I'm merely asking for
suggestions as to what to look at, etc. I'm going to set on some ethereal
monitoring of the traffic, and verify a few things on that end that seem
relatively obvious. Beyond that... ?
From: Vann H. Walke [mailto:walkev at presearch.com]
Sent: Wednesday, December 18, 2002 5:09 AM
To: John Hearns
Cc: Brian LaMere; beowulf at beowulf.org
Subject: Re: memory leak
I agree that this seems like the most likely source of your problem.
Unfortunately with the current Linux kernels obtaining clear memory
usage information is difficult. The only way I know to really test
memory usage is to write a simple program that attempts to malloc large
areas of memory - If the malloc succeeds, the memory wasn't really being
used. If you read back through the archives you should find some other
messages relating to the problem and perhaps even some test code.
On Wed, 2002-12-18 at 05:44, John Hearns wrote:
> Brian, please forgive me if I am insulting your intelligence.
> But are you sure that you are not just noticing the disk
> buffering behaviour of Linux?
> The Linux kernel will use up spare memory as disk buffers -
> leading an (apparently) lack of free memory.
> This is not really the case - as the memory will be released
> again when needed.
> (Ahem. Was caught out by this too the first time I saw it...)
> Anyway, if this isn't the problem, maybe you could send
> us some of the stats from your system?
> Maybe use nfsstat?
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