Date: Fri, 28 Nov 2003 21:32:30 -0400 (AST) From: "Marc G. Fournier" <scrappy@hub.org> To: freebsd-current@freebsd.org Cc: freebsd-stable@freebsd.org Subject: Time jumping on both 4.x and 5.x ... Message-ID: <20031128212342.G99096@ganymede.hub.org>
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This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. Send mail to mime@docserver.cac.washington.edu for more info. --0-464178111-1070069550=:99096 Content-Type: TEXT/PLAIN; charset=US-ASCII In trying to isolate an issue where the PostgreSQL 'explain analyze' is showing "odd results" (namely, negative time estimates on queries), Tom Lane wrote a quick C program to test gettimeofday() (program attached) ... the results on a 4.9-PRERELEASE kernel of Sep 20 14:16:48 ADT 2003 shows: neptune# time ./timetest out of order tv_sec: 1070068479 99040, prev 1070069174 725235 out of order tv_usec: 1070068479 99040, prev 1070069174 725235 out of order tv_sec: 1070069175 19687, prev 1070068479 99040 out of order tv_usec: 1070069175 19687, prev 1070068479 99040 out of order tv_sec: 1070068499 99377, prev 1070069194 625573 out of order tv_usec: 1070068499 99377, prev 1070069194 625573 out of order tv_sec: 1070069194 808542, prev 1070068499 99377 ^C1.171u 23.461s 0:24.68 99.7% 5+169k 1+0io 0pf+0w One person on the list has tried the same script on a 5.2 kernel, and reports seeing similar results, but after a longer period of time (~30min) ... In most (all?) cases, the offset appears to be ~+/-695 secs ... Linux ppl on the list, running the same problem, seem to be able to reproduce the issue, except they are only finding differences of 1 microsecond, and then only on older kernels (2.2.x, apparently) ... those running newer Linux kernels are reporting a clean run ... Known problem? ---- Marc G. Fournier Hub.Org Networking Services (http://www.hub.org) Email: scrappy@hub.org Yahoo!: yscrappy ICQ: 7615664 --0-464178111-1070069550=:99096 Content-Type: TEXT/PLAIN; charset=US-ASCII; name="timetest.c" Content-Transfer-Encoding: BASE64 Content-ID: <20031128213230.Q99096@ganymede.hub.org> Content-Description: Content-Disposition: attachment; filename="timetest.c" I2luY2x1ZGUgPHN0ZGlvLmg+DQojaW5jbHVkZSA8c3lzL3RpbWUuaD4NCg0K aW50DQptYWluKCkNCnsNCglzdHJ1Y3QgdGltZXZhbCBwcmV2dGltZTsNCglz dHJ1Y3QgdGltZXZhbCBjdXJ0aW1lOw0KDQoJZ2V0dGltZW9mZGF5KCZwcmV2 dGltZSwgTlVMTCk7DQoNCglmb3IgKDs7KQ0KCXsNCgkJZ2V0dGltZW9mZGF5 KCZjdXJ0aW1lLCBOVUxMKTsNCg0KCQlpZiAoY3VydGltZS50dl91c2VjIDwg MCB8fCBjdXJ0aW1lLnR2X3VzZWMgPj0gMTAwMDAwMCkNCgkJCWZwcmludGYo c3RkZXJyLCAiYm9ndXMgdHZfdXNlYzogJWxkICVsZCwgcHJldiAlbGQgJWxk XG4iLA0KCQkJCQkobG9uZyBpbnQpIGN1cnRpbWUudHZfc2VjLA0KCQkJCQko bG9uZyBpbnQpIGN1cnRpbWUudHZfdXNlYywNCgkJCQkJKGxvbmcgaW50KSBw cmV2dGltZS50dl9zZWMsDQoJCQkJCShsb25nIGludCkgcHJldnRpbWUudHZf dXNlYyk7DQoNCgkJaWYgKGN1cnRpbWUudHZfc2VjIDwgcHJldnRpbWUudHZf c2VjIHx8DQoJCQljdXJ0aW1lLnR2X3NlYyA+IHByZXZ0aW1lLnR2X3NlYyAr IDEpDQoJCQlmcHJpbnRmKHN0ZGVyciwgIm91dCBvZiBvcmRlciB0dl9zZWM6 ICVsZCAlbGQsIHByZXYgJWxkICVsZFxuIiwNCgkJCQkJKGxvbmcgaW50KSBj dXJ0aW1lLnR2X3NlYywNCgkJCQkJKGxvbmcgaW50KSBjdXJ0aW1lLnR2X3Vz ZWMsDQoJCQkJCShsb25nIGludCkgcHJldnRpbWUudHZfc2VjLA0KCQkJCQko bG9uZyBpbnQpIHByZXZ0aW1lLnR2X3VzZWMpOw0KDQoJCWlmIChjdXJ0aW1l LnR2X3VzZWMgPCBwcmV2dGltZS50dl91c2VjICYmDQoJCQljdXJ0aW1lLnR2 X3NlYyAhPSBwcmV2dGltZS50dl9zZWMgKyAxKQ0KCQkJZnByaW50ZihzdGRl cnIsICJvdXQgb2Ygb3JkZXIgdHZfdXNlYzogJWxkICVsZCwgcHJldiAlbGQg JWxkXG4iLA0KCQkJCQkobG9uZyBpbnQpIGN1cnRpbWUudHZfc2VjLA0KCQkJ CQkobG9uZyBpbnQpIGN1cnRpbWUudHZfdXNlYywNCgkJCQkJKGxvbmcgaW50 KSBwcmV2dGltZS50dl9zZWMsDQoJCQkJCShsb25nIGludCkgcHJldnRpbWUu dHZfdXNlYyk7DQoNCgkJcHJldnRpbWUgPSBjdXJ0aW1lOw0KCX0NCg0KCXJl dHVybiAwOw0KfQ0K --0-464178111-1070069550=:99096--
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