Date: Tue, 28 Oct 1997 13:29:17 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: tlambert@primenet.com (Terry Lambert) Cc: dyson@FreeBSD.ORG, tlambert@primenet.com, angio@angio.net, perlsta@cs.sunyit.edu, hackers@FreeBSD.ORG Subject: Re: help with fstat? Message-ID: <199710281829.NAA16590@dyson.iquest.net> In-Reply-To: <199710281704.KAA25457@usr06.primenet.com> from Terry Lambert at "Oct 28, 97 05:04:37 pm"
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Terry Lambert said: > > > > > There used to be a MAP_SEQUENTIAL flag to get it to discard buffers > > > > > after they had been accesed, instead of forcing more pages off the > > > > > LRU, but BSD doesn't support this. 8-(. > > > > > > > > > > > > > > Try madvise(2). It has a MADV_SEQUENTIAL. > > > > > > Is this supposed to cause it to discard page A after faulting in page B > > > on the assumption A will not be rereferenced? > > > > > > I didn't think that it did this in -current... > > > > It doesn't 'discard', but should either deactivate or cache the page. > > Then it leaves the machine with quickly faulted pages (no system call > overhead, like read/write would need, so faulting is "unfair") filling > the LRU, pushing off "good" pages in preference for "bad" pages. In > this case, "good" == "will be referenced again" and "bad" == "will not > be referenced again". > Pages are usually pretty darned unused by the time they are on the inactive or cache queues. -- John dyson@freebsd.org jdyson@nc.com
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