[PATCH] powerpc/powernv: Turn on SCSI_AACRAID in powernv_defconfig

[Michael Ellerman]

Brian King <brking at linux.vnet.ibm.com> writes:

> On 08/31/2017 07:37 AM, Michael Ellerman wrote:
>> Stewart Smith <stewart at linux.vnet.ibm.com> writes:
>> 
>>> Michael Ellerman <mpe at ellerman.id.au> writes:
>>>> OK. So maybe when the petitboot kernel moves up to 4.14 they may want to
>>>> flip it back to being a module.
>>>
>>> Yeah. We tend to keep all RAID adapters as modules because they almost
>>> all uniquely try to undo all boot time optimization done by anybody,
>>> anywhere, ever.
>> 
>> Yes I know what you mean. I am thinking of one In ParticulaR.
>
> Ouch. In all fairness over the life of ipr I've done a couple things to
> improve initialization time.

Sorry that wasn't meant as a dig at you, more the hardware. It might
have needed a smiley :)

> 1. On a PowerVM machine, the ipr boot device should not get reset between
>    the FCODE driver and the Linux driver, so init is extremely fast. If its
>    a non-boot device, then you'll have to wait for the firmware to initialize
>    on those adapters.

Yeah I don't see any problem on my LPARs, which just have a single IPR
for the boot device. Init takes ~1 second.

> 2. On a bare metal machine, if you set ipr.fast_reboot=1 on the skiboot
>    kernel, then we should also avoid resetting the ipr adapter, so ipr
>    init on the kernel being kexec booted from skiboot should be extremely fast. 

OK, I didn't know that was an option, so that might help.

> ...
> If you've got cases where ipr init is taking a long time, I'd be
> interested to know what scenarios are the most annoying to see if there
> is any opportunity to improve.

Yeah booting bare metal is where I see it (not using ipr.fast_reboot).

eg booting a Tuleta:

  [    1.517752] ipr: IBM Power RAID SCSI Device Driver version: 2.6.4 (March 14, 2017)
  ...
  [    1.519884] ipr 0001:08:00.0: Initializing IOA.
  [    1.519941] scsi host0: IBM 0 Storage Adapter
  [   25.695744] ipr 0001:08:00.0: Starting IOA initialization sequence.
  ...
  [   26.329614] sd 0:2:0:0: [sda] Spinning up disk...
  [   26.329752] sd 0:2:1:0: [sdb] Spinning up disk...
  [   26.329990] sd 0:2:2:0: [sdc] Spinning up disk...
  [   26.330065] sd 0:2:3:0: [sdd] Spinning up disk...
  ...
  [   26.349962] sr 0:0:6:0: Attached scsi generic sg15 type 5


Those 24 seconds are a bit of a shame. I assume we're just waiting for
the card firmware to come up?

I don't think there's much we can do in the kernel, PCI has just come
up, so we can't start the IPR init earlier. And the rest of the boot
only takes ~3 seconds, so even if we did everything else in parallel,
we'd still be waiting ~21 seconds for IPR.

cheers