Date: Fri, 16 Jul 1999 02:38:22 +0900 (JST) From: Noriyuki Soda <soda@sra.co.jp> To: freebsd-hackers@FreeBSD.ORG Cc: tech-userlevel@netbsd.org Subject: Re: Swap overcommit (was Re: Replacement for grep(1) (part 2)) Message-ID: <199907151738.CAA10933@srapc342.sra.co.jp> In-Reply-To: <Pine.GSO.3.95.990715082122.11860B-100000@jericho> References: <378D67B3.3E2A703C@newsguy.com> <Pine.GSO.3.95.990715082122.11860B-100000@jericho>
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> On Thu, 15 Jul 1999, Daniel C. Sobral wrote: >> Uh... like any modern unix, Solaris overcommits. >>>>> On Thu, 15 Jul 1999 08:46:36 -0700 (PDT), "Eduardo E. Horvath" <eeh@one-o.com> said: > Where do you guys get this misinformation? : > Note the `19464k reserved'; that space has been reserved but not yet > allocated. Both Dillon and Sobral mistakenly claimed that "Solaris overcommits", this fact seems to be somewhat suggestive. And also, the followings are allocated memory and reserved memory in my environment. (This table also includes Eduardo's example) SunOS allocated reserved total total/allocated ----- --------- -------- -------- ------------ 4.1.4 4268k 1248k 5516k 1.2924 4.1.2 7732k 1492k 9224k 1.193 4.1.4 8848k 3080k 11928k 1.3481 4.1.4 13532k 6772k 20304k 1.5004 5.5.1 15312k 5092k 20404k 1.3325 4.1.3 16112k 6512k 22624k 1.4042 4.1.2 26356k 1620k 27976k 1.0615 4.1.4 26560k 3756k 30316k 1.1414 5.5 26076k 11348k 37424k 1.4352 4.1.4 32984k 5556k 38540k 1.1684 5.6 32448k 7072k 39520k 1.2179 4.1.4 38056k 3692k 41748k 1.097 4.1.4 49064k 7672k 56736k 1.1564 4.1.4 67012k 7800k 74812k 1.1164 4.1.4 99348k 16956k 116304k 1.1707 4.1.4 118288k 11780k 130068k 1.0996 5.6 231968k 18880k 250848k 1.0814 5.7 307240k 19464k 326704k 1.0634 (sorted by total amount of used swap) In those examples, non-overcommiting system requires 1.06x ... 1.50x more swap space than overcommiting system. This table also indicates that in proportion as total used swap increase the ratio will decrease. And extra swap space required on non-overcommiting system is approximately several tens mega bytes. i.e. The extra cost of non-overcommiting system is less than ten dollers in my environment. Matt Dillon claimed that non-overcommiting system requires 8x or more swap space than overcommiting system. That's just wrong as above. (There might be cases which requires 8x swap, but it is not typical like Dillon said.) If you don't want non-overcommiting system, because you don't want to pay it's cost. That's OK, but please don't force us to accept your limited view. -- soda To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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