Subject: Re: How do I supress/shrink VM Page Cache for large files?
To: None <>
From: Ivo Vachkov <>
List: tech-kern
Date: 06/13/2003 13:04:49
der Mouse is right except for certain ocasions/enviroments where you
don't know when you'll need free memory pages. For example I can
point network appliances/dedicated devices. Assuming routing/
firewalling/accounting is the high-level priority job for this device you
should not let low-priority job (as logging) to interfere the productivity
of high-priority ones. Say, you have this logging software using all the
pages in the VM system and in a certain moment you have to process
some traffic in a "no free memory" enviroment. Starting VM/cache
syncroniztaion may degrade network performance, firewall processing,
So, my point is "It is a good idea to keep pages in memory when someone
will use them, except for the situations like the one described above"

	Ivo Vachkov
	Network Administrator
	Unilans Networking

der Mouse wrote:
>>>If you will *never* read it, I have to ask, why bother writing it?
>>Obviously its for logging as the poster said.
> Yes, but why bother writing logs that will never be read?
> (Actually, I got an off-list explanation: it _will_ be read, just not
> until much later, and then only to copy it off-machine.)
> My next question: are you sure you need to?  It's been a while since I
> worked with -current, but when I last did (mid-2002), it behaved as
> described - but the "duplicate" memory was reclaimed instantly as soon
> as anyone else wanted memory and there was none free.  After all, why
> not cache it until someone wants the pages?  Doesn't hurt anything, as
> long as you keep enough records to know the page can be thrown away
> instantly as soon as anyone wants it.
> /~\ The ASCII				der Mouse
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