Date: Thu, 10 Sep 2009 16:43:35 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: John Baldwin <jhb@freebsd.org> Cc: src-committers@freebsd.org, svn-src-stable@freebsd.org, svn-src-all@freebsd.org, svn-src-stable-8@freebsd.org, Ken Smith <kensmith@cse.buffalo.edu>, Ken Smith <kensmith@freebsd.org> Subject: Re: svn commit: r197065 - in stable/8: etc/defaults lib/libc/stdlib sys/amd64/conf sys/i386/conf sys/ia64/conf sys/pc98/conf sys/powerpc/conf sys/sparc64/conf Message-ID: <alpine.BSF.2.00.0909101641170.78984@fledge.watson.org> In-Reply-To: <200909101118.22525.jhb@freebsd.org> References: <200909101404.n8AE41C6021588@svn.freebsd.org> <200909101023.44913.jhb@freebsd.org> <1252593149.75144.18.camel@bauer.cse.buffalo.edu> <200909101118.22525.jhb@freebsd.org>
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On Thu, 10 Sep 2009, John Baldwin wrote: >> It has been pointed out to me on the mailing lists that leaving it on for >> stable/7 was an oversight, it is off on previous branches. >> >> I can understand the motivation for it. In a data center full of >> production machines crash dumps cause reboots to take longer and >> potentially cause disk space issues. In those sorts of environments it's >> best if by *default* the crash dumps don't happen and if an admin finds >> they need it they turn it on. >> >> This is one of those "There is no right answer" things... > > Hmm, I thought the crashdumps were a conscious descision as part of another > change in 7.x (shipping with debug symbols enabled by default) to try to > make it easier to get more useful crash reports from stock kernels. Having > the debug symbols present is probably enough for that though since it is > fairly easy to enable crashdumps in rc.conf vs. having to build a new kernel > just to get debug symbols. Should we change the default behavior in 7? I wonder if we could teach libkvm how to work directly from a crashdump in situ in the swap partition? This would not fix "slower reboot times" but it would help a lot with the "running out of disk space" thing. I see no reason at all we shouldn't be logging things like panics/stack traces for every crash in our normal logs -- in fact, that was much of the motivation for text dumps (and crashinfo too, no doubt): capture critical crash information in a compact way that can be e-maile around, etc, without the overhead of multi-gig dumps. Teaching libkvm how to work on crash dump partitions would let us avoid having the crashdump reside in the file system and help a lot with that problem. Robert N M Watson Computer Laboratory University of Cambridge
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