Date: Sat, 19 Nov 2005 02:35:52 +0100 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Johan =?iso-8859-2?Q?Str=F6m?= <johan@stromnet.org> Cc: freebsd-stable@freebsd.org, Michal Mertl <mime@traveller.cz>, delphij@delphij.net Subject: Re: Page fault, GEOM problem?? Message-ID: <20051119013552.GC735@garage.freebsd.pl> In-Reply-To: <BEE8C957-9DB5-4A08-AAAE-A1E524F4E092@stromnet.org> References: <991F35AA-151B-4AEA-82BD-5F4AEDF28424@stromnet.org> <a78074950511180117r6d64db25o4ae37c0c5998e002@mail.gmail.com> <74994962-5050-47BD-897B-DE3880B9EBD5@stromnet.org> <a78074950511180943r57fd9d03r64efcc705001bc35@mail.gmail.com> <A6F22EE2-B1E6-44B5-B4C2-E77E1A24FEBB@stromnet.org> <1132353600.903.19.camel@genius1.i.cz> <BEE8C957-9DB5-4A08-AAAE-A1E524F4E092@stromnet.org>
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--qjNfmADvan18RZcF Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Nov 19, 2005 at 01:55:57AM +0100, Johan Str=F6m wrote: +>=20 +> On 18 nov 2005, at 23.39, Michal Mertl wrote: +>=20 +> >Johan Str=F6m wrote: +> >>Hi! +> >> +> >>On 18 nov 2005, at 18.43, Xin LI wrote: +> >> +> >>>Hi, Johan, +> > +> >< large snip> +> > +> >>So, it seems it does run savecore after running dumpon and mounting +> >>disks etc... Is that wrong? +> > +> >No, this is normal. When you run savecore you need to have mounted +> >filesystems. In order to mount the filesystems they may have to be +> >checked. The fsck program requires big amount of memory to check larger +> >filesystems so the swap has to be enabled. Core dumps are written to the +> >dump device (swap) from the end whereas the swap is normally used from +> >the beginning (or the other way around). Therefore there's quite a big +> >chance that, even when the swap has to be used for fsck, the core dump +> >is intact and usable. If the usage of the swap file by fsck corrupts the +> >core dump you may start after next crash in single user mode and run the +> >commands manually (without enabling swap). +> > +> >As to why you can write kernel core dumps only to certain devices the +> >answer is that at the time, when the kernel is dumping core, it is +> >usually in pretty bad state, kernel internals may be corrupted and so +> >on. The dumping code is therefore written to be quite low level so that +> >even wedged kernel can be dumped. The dumping code is part of hard disk +> >controller's drivers. The gmirror is quite high-level device and geom +> >itself needs working scheduler so there will probably never be a way to +> >dump on gmirror provided swap. When you issue the dumpon command the +> >check is performed whether the driver for the disk you want to dump on +> >supports kernel core dumps. +> > +> >Michal +>=20 +> Well that makes sense... Then that is right at least.. :) +>=20 +> I just noticed another thing... My disk performance... sucks! :P +>=20 +> Some examples (from an otherwise unloaded system): +>=20 +> root@elfi:/home/johan$ time dd if=3D/dev/zero of=3Dbigfile.zero bs=3D102= 4 count=3D1000000 +> 1000000+0 records in +> 1000000+0 records out +> 1024000000 bytes transferred in 77.014797 secs (13296146 bytes/sec) You won't get more with such small block size. Try bs=3D128k. --=20 Pawel Jakub Dawidek http://www.wheel.pl pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! --qjNfmADvan18RZcF Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFDfoF4ForvXbEpPzQRAuu+AKCSKbx7lyVe/Z8exPROExZF5VTTiwCeNRCX MJcdDutI23IiKiK9XmsJA4Y= =y2nJ -----END PGP SIGNATURE----- --qjNfmADvan18RZcF--
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