Date: Wed, 5 Apr 1995 08:52:56 -0500 (CDT) From: bob@obiwan.pmr.com (Bob Willcox) To: davidg@Root.COM Cc: bde@zeta.org.au, hackers@FreeBSD.org Subject: Re: swap always use at least 64KB ? Message-ID: <m0rwVVw-00030oC@obiwan.pmr.com> In-Reply-To: <199504051101.EAA00175@corbin.Root.COM> from "David Greenman" at Apr 5, 95 04:01:43 am
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David Greenman wrote: > > >>>which is kind of curious, as the machine has 16 MB ram and almost > >>>no activity going on... Swap partition, when in use, are always > >>>reported with at least 64 KB in use. > >>> > >>>Is there any explaination ? > > > >> The first swap block is always pre-allocated. This was done to work around > >>a problem with people putting their swap partition at the beginning of their > >>disk (the system would happily try to destroy the label). I suppose it would > >>be better to change swapinfo/pstat to not include the first block of swap > >>space in its report. > > > >There must be bugs in the write protection of the label for that to happen. > > > >The diskslice "driver" snoops on writes to label sector(s) and rejects > >writing of invalid labels even when write protection is off. > > > >Similar snooping is required for protecting the MBR and secondary BR's. > > There were two manifestations. It would either destroy your label (I think > this was in the SCSI case) or it would get EROFS when the swap pager tried to > page something out to it. I think the 'destroy your label' problem was fixed > awhile ago. Now the pager just fails with the EROFS. ...Anyway, the first > chunk can't be used. Would this explain these errors (the EROFS on SCSI) on my 1.1.5.1 system? If so, are they harmful? I have been getting them for some time (since I added the disk with the swap partition starting at the beginning of the disk :-() but haven't been able to attribute any other problems to them. -- Bob Willcox bob@obiwan.pmr.com (or obiwan%bob@uunet.uu.net) Austin, TX
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