Date: Fri, 3 Oct 2008 13:26:17 +0100 From: RW <fbsd06@mlists.homeunix.com> To: freebsd-questions@freebsd.org Subject: Re: More RAM for buffers? Message-ID: <20081003132617.4c53001c@gumby.homeunix.com.> In-Reply-To: <200810020958.54563.kirk@strauser.com> References: <200810020958.54563.kirk@strauser.com>
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On Thu, 2 Oct 2008 09:58:54 -0500 Kirk Strauser <kirk@strauser.com> wrote: > I have an AMD system with 6GB of RAM. From dmesg: > > usable memory = 6428237824 (6130 MB) > avail memory = 6203797504 (5916 MB) > > However, most of it is just sitting there when it looks like it could > be used for buffers or cache: > > Mem: 1186M Active, 3902M Inact, 468M Wired, 233M Cache, 214M Buf, > 138M Free Swap: 8192M Total, 900K Used, 8191M Free > > Since I've yet to find a great explanation for what the different > types of memory are, could someone say why all that inactive memory > is better than using it for cache or buffers? The terms are a bit misleading, because the don't all relate to the use of the memory from the user's perspective, but how it's seen within FreeBSD's integrated cache/VM system. Active, Inact, Cache and Free are all part of the life-cycle of normal memory pages, they hold pretty much everything used by processes, and disk-caching. "Cache" actually has little to do with caching as such; it contains pages that are still holding data, but can be reused instantaneously because they are consistent with their backing store. In not exactly sure what "Buf" is, but I guess it's low-level disk buffering memory, that can't be discarded the way normal disk caching pages can.
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