Date: Wed, 28 Jun 1995 09:43:58 -0500 From: Mark Tinguely <tinguely@plains.nodak.edu> To: freebsd-questions@freebsd.org, rsnow@legend.txdirect.net Subject: Re: Swapinfo again (never decreases) Message-ID: <199506281443.JAA00651@plains.nodak.edu>
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you say : Step1: swapinfo says 0% used Step2: start X (or any big program) Step3: exit X (or the above mentioned large progra) Step4: swapinfo says 19% used at step2, your RAM is all being used, so some pages are forced to backstore. these pages will stay on backstore until the application for these pages is terminated. A while back I proposed and implemented removing the backstore pages when they were paged back back into RAM. those were the days when *BSD was hanging all the time due to swap depletion. I figure (still do) that things that were paged to backstore may not be the same pages forced back when RAM is depleted again, and we would be prematurely filling the swap and back then my counters determined that it was very seldon occurance that a read backstored page was ever put back into backstore without modifying the page. This idea of removing the backstore page when read from swap never sailed with the VM crew, especially when the VM storing and fetching was improved for FreeBSD. They wanted to keep these pages in swap as a cache. I guess I never fully understood that (not to say they are wrong, I just never heard the reasoning). --mark.
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