problems with AHCI on FreeBSD 8.2

[Victor Balada Diaz]

On Tue, Feb 14, 2012 at 03:09:58PM -0800, Jeremy Chadwick wrote:
> On Tue, Feb 14, 2012 at 11:15:27PM +0100, Victor Balada Diaz wrote:
> > On Tue, Feb 14, 2012 at 06:17:19PM +0100, Harald Schmalzbauer wrote:
> > >  schrieb Jeremy Chadwick am 14.02.2012 17:50 (localtime):
> > > > On Tue, Feb 14, 2012 at 04:55:10PM +0100, Claudius Herder wrote:
> > > >> Hello,
> > > >>
> > > >> I have got a quite similar problem with AHCI on FreeBSD 8.2 and it still
> > > >> persists on FreeBSD 9.0 release.
> > > >>
> > > >> Switching from ahci to ataahci resolved the problem for me too.
> > > >>
> > > >> I'm using gmirror for swap, system is on a zpool and the problem first
> > > >> occurred during a zpool scrub, but it is easily reproducible with dd.
> > > >>
> > > >> The timeouts only occur when writing to disks, dd if=/dev/ada{0|1}
> > > >> of=/dev/null is not an issue.
> > > >> Sometimes I need to power off the server because after a reboot one disk
> > > >> is still missing.
> > > >>
> > > >> I really would like to help in this issue, so let me know if you need
> > > >> any more information.
> > > > I find it interesting that, at least so far, the only people reporting
> > > > problems of this type with the ahci.ko driver are people using Samsung
> > > > disks.  The only difference is that your models are F1s while the OPs
> > > > are F2s.
> > > 
> > > I saw such timeouts long ago and mav@ had a look at my postings and he
> > > mentioned it could be a NCQ problem.
> > > I suspected the disks firmware.
> > > I never tracked it down further, because after replacing the Samsung (F3
> > > in that case) disks with hitachi ones solved all my problems and gave a
> > > big performance kick as well (with zfs).
> > > You can find the discussion here:
> > > http://lists.freebsd.org/pipermail/freebsd-stable/2010-February/055374.html
> > > 
> > 
> > You gave me a good idea: try to disable NCQ and see if that's the fault. So
> > i went and applied the attached patch. After it, i can no longer reproduce
> > the issue with ahci driver.
> > 
> > I know this is not a solution because it disables NCQ at controller level
> > instead of disk level, but at least we know for sure where the problem is.
> > 
> > I think the solution would be to add a new quirk ADA_Q_NONCQ in sys/cam/ata/ata_da.c.
> > Quirks infraestructure is already built, so adding a new quirk for this seems
> > easy.
> > 
> > Is someone interested? Do you think there is a better solution?
> > 
> > If someone is interested i can build a patch to add ADA_Q_NONCQ quirk and add my drives
> > to it.
> 
> I took a stab at this, but I don't feel confident this is the proper
> solution/method.  I worry there's some sort of chicken-or-the-egg
> condition here (quirk setup/matching comes *after* SATA capabilities
> detection), or that it makes the code messier.  Need mav@'s
> recommendations on this.
> 
> Below is for RELENG_8.  I should note I haven't tested if this works, or
> even compiles -- normally I don't provide such patches without testing
> so I apologise in advance / user beware.

You're amazingly fast. Thanks for all your help :)

You start applying the quirks before 

        snprintf(announce_buf, sizeof(announce_buf),
            "kern.cam.ada.%d.quirks", periph->unit_number);
        quirks = softc->quirks;
        TUNABLE_INT_FETCH(announce_buf, &quirks);

So you're breaking quirk setting at boot time.

See my attached patch. I can confirm it works for me.

Regards.

-- 
La prueba más fehaciente de que existe vida inteligente en otros
planetas, es que no han intentado contactar con nosotros. 
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