Date: Thu, 11 Apr 2002 08:10:44 -0400 From: Brian T.Schellenberger <bts@babbleon.org> To: Patrick Thomas <root@utility.clubscholarship.com>, <freebsd-questions@FreeBSD.ORG> Subject: Re: interpreting `top` output... Message-ID: <20020411121045.2E80CBA05@i8k.babbleon.org> In-Reply-To: <20020411011600.C77505-100000@utility.clubscholarship.com> References: <20020411011600.C77505-100000@utility.clubscholarship.com>
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On Thursday 11 April 2002 04:17 am, Patrick Thomas wrote:
| I see this memory summary in `top`:
|
| Mem: 431M Active, 1231M Inact, 277M Wired, 61M Cache, 199M Buf, 12M Free
|
|
| Does the 1231M Inact mean that I can basically fill up another 1.2gigs of
| memory with programs, etc., before I start running out of memory ?
Yes.
| Also, should I be concerned that I only have 12M "Free", or is the fact
| that so much (1231M) is inactive mean that I am not running out for a long
| time ?
The latter.
"Inactive" memory is memory that the O/S could reclaim but it keeps it around
"just in case" somebody happens to need it again.
Mostly, I speculate, this would be memory that was diskmapped read-only
(mostly code that has finished running)--so if somebody happens to re-map the
same disk space (as in re-running the program), it can be used again, thus
speeding things up quite a bit. It is certainly quite noticable under
FreeBSD that if you invoke a large program that pulls in lots of dynamic
libraries it loads *much* faster the second time, and I believe that the
concept of "inactive" memory is what causes this to occur.
I'm not sure about the last point, but I do know that inactive memory is
effectively free and that it tends over time to never go down. (I run
xosview all the time, so memory patterns are very visible to me, and the
pattern is clear: over time, the (acitve+inactive) memory normally only goes
up--sort of like a fever thermometer--but the active memory takes up a
variable amount of the (active+inactive) total. The only exception being
that if memory gets really tight, and the inactive memory gets all used up,
then sometimes when memory gets freed again the (active+inactive) amount will
wind up being lower. Usually when this happens, some swap winds up getting
consumed, but I don't believe that this is always the case.
| thanks,
|
| PT
|
|
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--
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