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Date:      Thu, 2 Oct 2008 14:09:56 -0400
From:      "Josh Carroll" <josh.carroll@gmail.com>
To:        "Bill Moran" <wmoran@potentialtech.com>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: More RAM for buffers?
Message-ID:  <8cb6106e0810021109m7a82d3d3j7e29f9e0ba406e13@mail.gmail.com>
In-Reply-To: <20081002131435.efa1d07f.wmoran@potentialtech.com>
References:  <200810020958.54563.kirk@strauser.com> <200810021004.56210.kirk@strauser.com> <20081002131435.efa1d07f.wmoran@potentialtech.com>

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> inactive, cache, and buffer are all different types of "buffer".

That is my understanding as well.

> I'm fairly sure that inactive is memory used by program code.  When the
> program terminates, the memory is marked as inactive, which means the
> next time the program starts the code can simply be moved back to
> active and the program need not be reloaded from disk.

I think non-program code can also be "inactive".

For example, top memory output before:

Mem: 337M Active, 1455M Inact, 407M Wired, 352K Cache, 214M Buf, 1745M Free

and after:  find /usr/src -type f -print0 | xargs -0 cat > /dev/null 2>&1

Mem: 348M Active, 1905M Inact, 402M Wired, 912K Cache, 214M Buf, 1288M Free

I am also not sure exactly what constitutes each of these. I only know
what the top man page says. And for Buf it says:

       Buf:   number of pages used for BIO-level disk caching

I'm not entirely sure what "BIO-level disk caching" is, but it is
apparently NOT the caching of filesystem data.

Josh



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