Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83 (MC840302); site sal.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!mcvax!enea!sal!jf From: jf@sal.UUCP (Johan Finnved) Newsgroups: net.unix-wizards Subject: Re: Do inter-process pipes use secondary (disc) memory for buffering? Message-ID: <542@sal.UUCP> Date: Tue, 21-May-85 01:01:28 EDT Article-I.D.: sal.542 Posted: Tue May 21 01:01:28 1985 Date-Received: Thu, 16-May-85 22:00:11 EDT References: <605@homxb.UUCP> <5566@umcp-cs.UUCP> Reply-To: jf@sal.UUCP (Johan Finnved) Distribution: net.unix Organization: Objecta, Taby, Sweden Lines: 17 Summary: The cache doesn't avoid disc writes on Version 7 In article <5566@umcp-cs.UUCP> chris@umcp-cs.UUCP (Chris Torek) writes: >> .. whether interprocess pipes use primary (main) or secondary (disc) memory > >The answer is "yes" and "yes". >... However, in most cases the data in pipes never gets out of the block >file system buffer cache (main memory). > Version 7 does a poor job at avoiding disc writes when using pipes: Whenever a write operation fills up a buffer a write is started even though the odds are high that the data will soon be read and no longer needed. Moreover when pipe reads have consumed a buffer it does not clear the B_DELWRI bit so delayed writes of no longer referenceable data happen. So using a pipe usually creates writes but seldom reads. Are later versions different ? Johan Finnved, Objecta, Sweden