Date: Thu, 27 Jan 2011 12:08:10 -0700 From: Warner Losh <imp@bsdimp.com> To: "Robert N. M. Watson" <rwatson@FreeBSD.org> Cc: src-committers@FreeBSD.org, Pawel Jakub Dawidek <pjd@FreeBSD.org>, John Baldwin <jhb@FreeBSD.org>, Ken Smith <kensmith@buffalo.edu>, Alexander Motin <mav@FreeBSD.org>, svn-src-projects@FreeBSD.org Subject: Re: svn commit: r217828 - projects/graid/head/sys/geom/raid Message-ID: <4D41C29A.5020100@bsdimp.com> In-Reply-To: <7FD27004-581F-4FED-858D-5819562CF111@freebsd.org> References: <201101251534.p0PFY7cF039182@svn.freebsd.org> <4D3FED31.8040304@FreeBSD.org> <1296054407.19051.5.camel@bauer.cse.buffalo.edu> <201101261042.38218.jhb@freebsd.org> <7FD27004-581F-4FED-858D-5819562CF111@freebsd.org>
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On 01/26/2011 08:45, Robert N. M. Watson wrote: > On 26 Jan 2011, at 15:42, John Baldwin wrote: > >> On Wednesday, January 26, 2011 10:06:47 am Ken Smith wrote: >>> On Wed, 2011-01-26 at 11:45 +0200, Alexander Motin wrote: >>>> Those who want maximum robustness should use dedicated >>>> drive on the most trivial dedicated controller to make dumping reliable. >>>> If we are going above that - there are always some compromises. >>> Please remember this statement when I change dumpdev from "AUTO" >>> to "NO" in /etc/defaults/rc.conf shortly after branching stable/9. :-) >> No, I still think this is the wrong answer. Kernel dumps are not inherently >> unreliable to the point that we should not enable them by default. However, >> turning dumps off is a good way to prevent developers from debugging non- >> trivial bugs that are only triggered under real-world workloads. >> >> I think we should strive to make our dumps as reliable as possible, but >> nothing in our system is perfect (hence bugs), and if we are going to require >> absolute perfection for kernel dumps before enabling them by default then we >> might as well not ship anything at all as I can _ensure_ you the rest of the >> system we ship is _not_ absolutely perfect. > I think the real constraint on shipping with dumps enabled remains a disk space consideration. If you have a problem triggering a kernel bug, you're going to generate quite a few crash dumps in short order, and for many users, that result is not good. But the answer there may be better savecore behaviour: perhaps we should keep the last (n) (where n is small -- perhaps 2) dumps by default, with a way to mark dumps that should be saved longer. minidumps have made the world better in some ways, I can't help wonder whether that could be refined further... I don't suppose there's a way that savecore could be hacked to convert a 'full' dump into a 'mini' dump? Warner
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