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Re: bdflush or others affecting disk cache

On Tue, 2004-04-20 at 03:55, David Wilk wrote:
> I'm going to have to disagree with the above poster.  This VM behavior
> is not ideal and is really counter-productive.  2.4.x saw lot's of VM
> work to improve performance over broad ranges of work-load.  The
> problems occur when changes are made for corner-cases and some more
> mainstream workloads suffer.

In my defence, I did say that linux VM has a history VM fixes and
rewrites in attempts to best tune behaviour. I did suggest that the
problem he was seeing was the 2.4.20 VM not doing a good job.

I totally agree that most of the linux VM problems have been caused by
trying to be too smart. I'm not an expert, but every time I've read
threads on it I've thought "Man, haven't you guys ever heard of KISS".

However, I think that it does make sense to swap out "dead code" to make
room for buffer space. You just need to make sure it's done right :-)

> on your question of running w/o swap space I will answer: NOT ON YOUR
> LIFE!  you should *never* run any kind of server w/o swap unless you
> don't mind processes randomly dying because OOM killer decides they
> should go for the sake of the system...

Even in systems with with bucket-loads of RAM, adding swap can make your
system faster. "dead code" can be swapped out, making room for more
buffer space. (ducks to avoid argument about VM tuning :-)

> so, for the sake of your sanity (and the security of your system)
> upgrade to 2.4.26 and re-enable swap!

Yeah. There are also security problems with 2.4.20 that have been fixed
in 2.4.26

Donovan Baarda <abo@minkirri.apana.org.au>

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