Date: Thu, 10 Jun 2010 20:58:32 +0300 From: Andriy Gapon <avg@icyb.net.ua> To: Gary Palmer <gpalmer@freebsd.org> Cc: freebsd-fs@freebsd.org Subject: Re: Odd network issues on ZFS based NFS server Message-ID: <4C1127C8.9040207@icyb.net.ua> In-Reply-To: <20100610173629.GA70716@in-addr.com> References: <20100608083649.GA77452@fupp.net> <Pine.GSO.4.63.1006081946040.8742@muncher.cs.uoguelph.ca> <20100609122517.GA16231@fupp.net> <Pine.GSO.4.63.1006091119410.23896@muncher.cs.uoguelph.ca> <20100610111316.GB87243@fupp.net> <20100610114614.GA71432@icarus.home.lan> <20100610173629.GA70716@in-addr.com>
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on 10/06/2010 20:36 Gary Palmer said the following: > On Thu, Jun 10, 2010 at 04:46:14AM -0700, Jeremy Chadwick wrote: >> Clarification: I believe it actually has 1927MB (147M Inact + 1780M >> Free) available. I've always understood top's "Free" field to mean >> "number/amount of pages which have never been touched/used since the >> kernel was started", while "Inact" to mean "number/amount of pages which >> have been touched/used but are not actively being used, this available >> for use". >> >> If someone more familiar with the VM and top could expand on this, >> that'd be helpful. > > I'm not a VM guru, however here is my understanding: > > - "Free" are pages that have been reclaimed by the page daemon and are > ready for immediate use without further action. The page daemon always > tries to keep a few pages in the "Free" state to avoid problems with > page starvation > > - "Inactive" pages are pages that are candidates for reclamation by the > page daemon if so needed. I believe some amount of work is needed to > move an inactive page to the free list, including zeroing it I think as > well as removing any references still pointing to it (e.g. it could be > a cached copy of data from local storage). Something like that, right. My understanding: Active pages are also candidates for reclamation, but Inactive are the primary ones. The only difference is how much time passed since they were last "referenced". Cached pages are pages that effectively free, i.e. can be reclaimed any moment, but their content is still valid and so they can be re-used. -- Andriy Gapon
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