Date: Tue, 03 Nov 1998 01:05:58 -0800 From: David Greenman <dg@root.com> To: "William S. Duncanson" <caesar@starkreality.com> Cc: freebsd-current@FreeBSD.ORG Subject: Re: Err...something fishy going on in top. Message-ID: <199811030905.BAA13428@implode.root.com> In-Reply-To: Your message of "Tue, 03 Nov 1998 00:05:40 CST." <4.1.19981102235947.052f0100@fire.starkreality.com>
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>I rebuilt world a couple of hours ago, from a cvsup at around 8:30 CST >tonight. When I rebooted, the box seemed slower than it should have been. >To make a long story short, in the process of doing stuff, I noticed that >whenever there's heavy disk i/o, instead of the amount of memory dedicated >to cache increasing, the amount of memory being listed as inactive was >increasing. Huh? I'm confused. Right now, it looks like none of my >memory is being used for file cacheing, even though I have > 32 MB free. >What am I missing? You're missing what it all actually means. "cache" is a queue, not an indication of caching. The same is also true for "active", "inactive", and "free" - they are just various page queues that the system moves pages between depending on their priority. A change was made recently so that cached file pages are always put onto the inactive queue rather than just some of the time (they previously would also be put onto the cache queue). This actually improves performance because it keeps the pages better LRU sorted. When memory becomes short, the pagedaemon will move the pages to the cache queue (and then to the free queue) as needed. This will not significantly increase CPU usage and will increase overall system performance by a measurable amount. -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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