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SubjectRe: What version of the kernel fixes these VM issues?
Date
On August 24, 2001 10:47 am, Anwar P wrote:
> We have big system (8 processors, 8GB ram), running Oracle and this other
> ETL tool. Oracle is up and running all the time, and the ETL tool runs
> once a day. But everytime the ETL tool runs (along with Oracle), the
> system seems to run out of memory, and the server comes to a crawl, often
> with keyborad response in 10 to 15 minute intervals. We are currently
> using the 2.4.3-6 kernel that comes with Redhat 7.1.
>
> We know that Oracle comsumes no more than 2GB of memory at peak usage, and
> the ETL tool itself consumes less than 1GB. But the ETL tool does process
> a whole bunch of text files (total about 6GB worth of), and it runs for
> about 2 hours. What happens is that while they are both running, the
> filesystem cache size increases progressively, and some time later, it
> begins swapping. We do have 16GB (2x RAM) of swap. And when it starts to
> swap, the server responds to keystrokes/commands randomly and appears dead
> for 10s of minutes. We know that together our applications do not need more
> than 4GB of RAM on this 8GB box, so it is the VM that is causing this
> unnecessary swapping by trying to use too much memory for filesystem cache.

There is no way your system should be going into swap under these conditions
- it's a bug. We have probably fixed this already.

> So the first question is, is there any way I can limit the amount of memory
> used for FS cache ?

Um, no, sorry. This should not be necessary.

> And the next one is, are there any (later) versions of the kernel that are
> more sane about what the maximum FS cache it should use is ?

Please try 2.4.9 and 2.4.8-ac10. If the system slows down, look in your logs
and see if there are any "allocation failed" messages. Use top or do watch
cat /proc/meminfo to be sure your system isn't going into swap, and please
let us know what happens.

--
Daniel
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