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Date:      Wed, 8 Mar 2006 20:52:57 +0300
From:      "Eugene" <genie@geniechka.ru>
To:        <dgw@liwest.at>, <freebsd-questions@freebsd.org>
Subject:   Re: Strange memory problems
Message-ID:  <002001c642d9$320fcab0$1b12c055@genie>
References:  <005b01c642bb$23e007c0$1b12c055@genie> <200603081756.36597.dgw@liwest.at>

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>> With Apache stopped, it goes down to RSS=0.5GB and VSZ=0.6G -- but 
>> Inactive
>> Memory remains above 2.5GB.
>> Is it a memory leak somewhere or what?
>
> That looks quite normal to me, apart from the zombie process. FreeBSD 
> always
> attempts to occupy most of the RAM, because it's a very fast way of saving
> information, and after all a lot of RAM is of no use if there's nothing in
> it. So long as no other program needs it for more "important" information,
> there's nothing wrong with keeping a lot of "unimportant" stuff around in
> case it is needed again quickly.

Ok, that's nice. However, I was concerned not so much with low Free memory 
as with Act+Inact being 1.5-4 times greater than size of running processes. 
What data is there, exactly? I don't think it has more than 1GB of unsynced 
disk writes?

Also, a more general question: how do I estimate 'real' memory load? 
Sum(RSS) + 0.5*DiskCache  ?
For example, I would like to know (in advance) e.g. how many Apache 
processes we can handle before memory becomes a problem.
Do you think it would be nice if top(1) could give some consolidated 
measure -- probably taking into account usage statistics and/or response 
time?
Or at least two measures -- e.g. "How much memory can be allocated off-hand 
without any disk I/O" and "How much memory can be allocated so that swapped 
data would not have to be re-read again in reasonable time"?

Thanks a lot
Eugene 




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