Re: qemu emulated machine crashes due to disk timeouts

[Paul Ripke <stix%stix.id.au@localhost>]

On Thu, May 14, 2020 at 03:32:51PM +0200, Jaromír Doleček wrote:
> Le jeu. 14 mai 2020 à 15:19, <maya%netbsd.org@localhost> a écrit :
> > > Bumped ATA_DELAY to 30000 (was 10000), and the VM stayed up overnight,
> > > only logging the one correctable soft error:
> > >
> > > May  7 04:19:29 qemu /netbsd: [ 16290.3345912] autoconfiguration error: piixide0:0:0: lost interrupt
> > > May  7 04:19:29 qemu /netbsd: [ 16290.3345912]  type: ata tc_bcount: 512 tc_skip: 0
> > > May  7 04:19:29 qemu /netbsd: [ 16290.3345912] autoconfiguration error: piixide0:0:0: bus-master DMA error: missing interrupt, status=0x21
> > > May  7 04:19:29 qemu /netbsd: [ 16290.6088515] wd0a: DMA error writing fsbn 1801813 (wd0 bn 1801876; cn 879 tn 52 sn 20), xfer 38, retry 0
> > > May  7 04:19:29 qemu /netbsd: [ 16292.6053372] wd0: soft error (corrected) xfer 38
> > >
> > > Would making ATA_DELAY configurable via options(4) be worth it?
> >
> > QEMU emulation isn't a niche setup, we should aim to have it work out of
> > the box without adjusting sysctls, IMO.
> 
> I agree. Let's fix QEMU IDE emulation?

I don't know that there's anything specifically wrong with the qemu
emulation - perhaps the fact that slow host I/O triggers PCI timeouts
and missed interrupts in the VM?

The reason I'm seeing issues is mostly due to the fact my machine has
a mirrored pair of slow WD Green disks, and runs a bunch of junk.
At times (esp overnight), I/O bogs down badly, and I hit the current
10s timeouts.

> Seriously though I think that it wouldn't hurt to just bump ATA_DELAY
> to 30 seconds by default.
> 
> Also as another general suggestion - you'll generally get more
> performance by using the PV drivers i.e. virtio, or ahcisata
> emulation.
> 
> Jaromir

-- 
Paul Ripke
"Great minds discuss ideas, average minds discuss events, small minds
 discuss people."
-- Disputed: Often attributed to Eleanor Roosevelt. 1948.