Date: Thu, 02 Dec 1999 14:05:01 -0800 From: Mike Smith <msmith@freebsd.org> To: mjacob@feral.com Cc: "Kenneth D. Merry" <ken@kdm.org>, Stephen McKay <syssgm@detir.qld.gov.au>, freebsd-scsi@FreeBSD.ORG Subject: Re: Tape driver problems Message-ID: <199912022205.OAA00570@mass.cdrom.com> In-Reply-To: Your message of "Thu, 02 Dec 1999 10:20:19 PST." <Pine.BSF.4.05.9912021019270.369-100000@semuta.feral.com>
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> > > > Dec 3 00:44:36 bucket /kernel: bus_dmamap_load: Too many segs! buf_len = 0x3000 > > > > > > > > The last bit changes. I've seen 0xb000 or 0xd000 or 0xe000 or 0xf000 also. > > > > This is a new problem related to the density autodetection read. I expect > > > > that an aha1542B just can't read MAXPHYS bytes from anything. > > > > > > Hmm, indeed. The density determining code does indeed issue a read of > > > MAXPHYS bytes. It seems to me that all HBA's should at least support that! > > > The maintainer for the 1542X will have to speak to this tho... > > > > I'm not the aha maintainer (Warner is), but I do know that it cannot do > > more than 64K at a time. So you shouldn't be using any more than that. > > Nonsense. That's what bounce buffers can or *should* be used for too. In this case, the problem is that the bounce buffer code has attempted to allocate space for the transfer, but it's sufficiently physically fragmented that it requires too many s/g entries to describe it. Either the aha code needs to be fixed to allow more s/g entries, or the bounce buffer code needs to be fixed to allocate things in larger chunks and thus keep fragmentation down, or we should just abandon these useless 10-year-old ISA SCSI controllers and worry about more useful things. 8) -- \\ Give a man a fish, and you feed him for a day. \\ Mike Smith \\ Tell him he should learn how to fish himself, \\ msmith@freebsd.org \\ and he'll hate you for a lifetime. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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