Date: Sat, 9 Feb 2008 07:41:08 +1100 From: Peter Jeremy <peterjeremy@optushome.com.au> To: "Carlos A. M. dos Santos" <unixmania@gmail.com> Cc: freebsd-stable@freebsd.org Subject: Re: RELENG_7: interrupt eating whole cpu core Message-ID: <20080208204107.GG4008@server.vk2pj.dyndns.org> In-Reply-To: <e71790db0802071822l661bdcb8s6dfe5b94be11f0dc@mail.gmail.com> References: <47A9F835.1060200@bsdforen.de> <47AA0696.5020109@bsdforen.de> <7872AB6E-21DA-4E2D-93C0-D07CFA3A7E47@mac.com> <47AA0E3E.4020304@bsdforen.de> <e71790db0802071822l661bdcb8s6dfe5b94be11f0dc@mail.gmail.com>
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--+mr2ctTDD1GjnQwB Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Feb 08, 2008 at 12:22:38AM -0200, Carlos A. M. dos Santos wrote: >Wow, now I'm *really* surprised. I used to think that putting > > hw.ata.ata_dma=3D"1" > hw.ata.atapi_dma=3D"1" hw.ata.ata_dma has no effect on ATAPI devices. >in /boot/loader.conf would be enough to enable DMA mode. Looking at the code, atapi_dma will enable UDMA modes if the drive supports at least UDMA2 them but ignores WDMA capabilities. This was part of the ATA mkIII update - which is in 6.x but was not MFC'd to 5.x. If you do a verbose boot, you will get a probe line reporting the drive capabilities. Unfortunately, atacontrol only reports 'dma [not] supported' - not what capabilities the drive has. >1. Is this related to using atapicam? No. >2. Should this be considered a bug? Possibly. The relevant commit message doesn't mention the ATAPI DMA changes so it's not clear whether this is an oversight or deliberate. I do recall that there have been problems in the past with ATAPI drives that would advertise DMA capabilities but would misbehave if you used DMA (atapi_dma was disabled by default in 5.x for this reason). I'm not sure if the current code is at effort to avoid this. --=20 Peter Jeremy Please excuse any delays as the result of my ISP's inability to implement an MTA that is either RFC2821-compliant or matches their claimed behaviour. --+mr2ctTDD1GjnQwB Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4 (FreeBSD) iD8DBQFHrL5j/opHv/APuIcRAsMpAJ9J6MNX0fu10xG+msFVbb6HPQu2KwCeP30i kw5LNtRaCsy5CvHXyzHeKWo= =Uxbb -----END PGP SIGNATURE----- --+mr2ctTDD1GjnQwB--
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