Date: Wed, 26 Jan 2011 15:45:34 +0000 From: "Robert N. M. Watson" <rwatson@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: svn-src-projects@freebsd.org, Alexander Motin <mav@freebsd.org>, src-committers@freebsd.org, Pawel Jakub Dawidek <pjd@freebsd.org>, Ken Smith <kensmith@buffalo.edu> Subject: Re: svn commit: r217828 - projects/graid/head/sys/geom/raid Message-ID: <7FD27004-581F-4FED-858D-5819562CF111@freebsd.org> In-Reply-To: <201101261042.38218.jhb@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>
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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... Roberthelp
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