Date: Tue, 20 Jan 2009 19:06:10 +0000 (UTC) From: Peter Holm <pho@FreeBSD.org> To: src-committers@freebsd.org, svn-src-projects@freebsd.org Subject: svn commit: r187479 - projects/stress2 Message-ID: <200901201906.n0KJ6AIH053925@svn.freebsd.org>
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Author: pho Date: Tue Jan 20 19:06:10 2009 New Revision: 187479 URL: http://svn.freebsd.org/changeset/base/187479 Log: Added comment about the non-deterministic feature of the test. Approved by: kib Modified: projects/stress2/README Modified: projects/stress2/README ============================================================================== --- projects/stress2/README Tue Jan 20 19:01:59 2009 (r187478) +++ projects/stress2/README Tue Jan 20 19:06:10 2009 (r187479) @@ -37,3 +37,23 @@ The following sub-directories exists: The name stress2 indicates that this is the second generation of the Kernel Stress Test Suite. The first version (stress) was based mostly on scripts. + + +20090120: des@ pointed out it would be nice to be able to set the + random seed in order to be able to reproduce errors in time. + A test of this show that the occurrence of panics are still + non-deterministic even with a fixed seed. The known broken + unionfs was used to test this: + http://people.freebsd.org/~pho/stress/log/marcus006.txt. + First panic occurred after 29 loops and the second after 8 + with a seed of "123". + + The randomness that is provided by lack of synchronization + with timer interrupt, disk block layout and disk access + latencies caused by platter and heads speed changes, disk + firmware internal operations, and so on are _much_ bigger + then the undeterminism caused by the non-repeatable random + seed. + + Anyway, I have always view the this issue as only a slight + inconvenience.
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