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Date:      Thu, 29 Jun 2000 19:16:54 +0200 (CEST)
From:      Paul Herman <pherman@frenchfries.net>
To:        Kenneth Wayne Culver <culverk@wam.umd.edu>
Cc:        Sam Xie <sam@samxie.cl.msu.edu>, freebsd-questions@FreeBSD.ORG
Subject:   Re: memory leak?
Message-ID:  <Pine.BSF.4.21.0006291901380.828-100000@bagabeedaboo.security.at12.de>
In-Reply-To: <Pine.GSO.4.21.0006291210440.9768-100000@rac10.wam.umd.edu>

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On Thu, 29 Jun 2000, Kenneth Wayne Culver wrote:

> > > Well, I know for sure that netscape leaks memory, but not that
> > > much, for most purposes though, the "inactive" memory is free for
> > > use by other programs, it's just being kept as inactive because
> > > some program stored in that memory that has exited might be run
> > > [...]
> > 
> > I think you are thinking about "cache" memory.  As far as I understand
> > it, "inactive" memory is just "active" memory that hasn't been used in
> > 30 seconds i.e. dirty pages that are still associated with objects and
> > cannot be reused until they are cleaned or freed (i.e. moved into
> > either "cache" or "free".)  At least, that's how I've understood it.
> > 
> Hrmm, I don't know, One thing I do know however is that when wmmon and
> other utilities that put guages on memory usage measure the usage, they
> measure inactive memory as free...

That'll teach me to open my mouth before looking at the code. :)  You
are right, inactive memory is free to use by other programs.  
However, only a small portion of the pages are usually clean for
immediate use.

As for the 30 seconds stuff, I don't know where the heck I read
that....  (search, search...)  Aha!  The vmstat(8) manpage it talks
about active memory being memory "belonging to processes which are
running or have run in the last 20 seconds."

So, I suppose in user land, there are conflicting definitions of what
active memory is, but in kernel land, it is indeed as you say.

-Paul.



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