Re: 9.1: boot-time delay?

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>> Will HZ=1000 be sufficient and does that reduce the boot time?
> The latter is a good question which is likely to hint at possible
> causes.  I'll experiment with various HZ values and see what happens.

At HZ=8000, the delay (based on the bracketed numbers) is almost
exactly 22 seconds.

At HZ=4000, it's almost exactly 10 seconds.

At HZ=2000, it's almost exactly 4.3 seconds.

Based on a quadratic fit to those three data points, all I need to do
is set HZ to 0 and it will reach the rest of the boot 1.2 seconds
before it gets to uhub3.  Clearly, this machine includes resublimated
thiotimoline somewhere in its hardware makeup.

Seriously, though...

I've just heard from one of the other people working with this.  I was
told that, on a different hardware platform, the delay is gone even
with HZ=8000.  I have an instance of that platform among my development
machines; I tried it and I see the same thing, even with a bit-for-bit
identical kernel.

I spent a little time playing with boot -c and disabling various
things, as suggested by Martin Husemann upthread.

Disabling ehci* (what that hardware uses for USB) shuts off all USB
support, of course.  It does nothing for the delay.

Disabling piixide* still gets the delay, but it also still finds wd0;
it just attaches pciide* instead of piixide*.

Disabling both piixide* and pciide* gets rid of wd* _and_ gets rid of
the delay.  (It doesn't boot fully, of course, beause it has no root
device.  But it reaches the root device prompt after some four seconds
instead of 25-plus.)

Disabling wd does not fix the delay, but it doesn't completely
eliminate wd; I still see "wd at ... not configured" messages, so it's
found in some sense.  (I haven't tried completely removing wd from the
kernel config.)

The machine without the delay has wd drives, but they attach at
ahcisata instead of piixide/pciide.  The piixide attachment (the
machine that exhibits the delay) is

piixide0 at pci0 dev 31 function 2: Intel 6 Series Serial ATA Controller (rev. 0x05)
piixide0: bus-master DMA support present
piixide0: primary channel configured to native-PCI mode
piixide0: using ioapic0 pin 19 for native-PCI interrupt
atabus0 at piixide0 channel 0
piixide0: secondary channel configured to native-PCI mode
atabus1 at piixide0 channel 1
...
piixide1 at pci0 dev 31 function 5: Intel 6 Series Serial ATA Controller (rev. 0x05)
piixide1: bus-master DMA support present
piixide1: primary channel wired to native-PCI mode
piixide1: using ioapic0 pin 19 for native-PCI interrupt
atabus2 at piixide1 channel 0
piixide1: secondary channel wired to native-PCI mode
atabus3 at piixide1 channel 1
...
wd0 at atabus0 drive 0
wd0: <ST500DM002-1BD142>
wd0: drive supports 16-sector PIO transfers, LBA48 addressing
wd0: 465 GB, 969021 cyl, 16 head, 63 sec, 512 bytes/sect x 976773168 sectors (0 bytes/physsect; first aligned sector: 8)
wd0: 32-bit data port
wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 5 (Ultra/100), WRITE DMA FUA, NCQ (32 tags)
wd0(piixide0:0:0): using PIO mode 4, Ultra-DMA mode 5 (Ultra/100) (using DMA), WRITE DMA FUA EXT
wd1 at atabus2 drive 0
wd1: <SATADOM-SV 3ME3>
wd1: drive supports 1-sector PIO transfers, LBA48 addressing
wd1: 7641 MB, 15525 cyl, 16 head, 63 sec, 512 bytes/sect x 15649200 sectors
wd1: 32-bit data port
wd1: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133), WRITE DMA FUA, NCQ (32 tags)
wd1(piixide1:0:0): using PIO mode 4, Ultra-DMA mode 6 (Ultra/133) (using DMA), WRITE DMA FUA EXT

In contrast, the ahcisata attachment, on the machine with no delay, is

ahcisata0 at pci0 dev 23 function 0: vendor 8086 product a102 (rev. 0x31)
ahcisata0: 64-bit DMA
ahcisata0: AHCI revision 1.31, 4 ports, 32 slots, CAP 0xe734ff43<EMS,PSC,SSC,PMD,SAM,ISS=0x3=Gen3,SCLO,SAL,SALP,SSNTF,SNCQ,S64A>
ahcisata0: interrupting at msi1 vec 0
atabus0 at ahcisata0 channel 0
atabus1 at ahcisata0 channel 1
atabus2 at ahcisata0 channel 2
atabus3 at ahcisata0 channel 3
...
ahcisata0 port 0: device present, speed: 6.0Gb/s
ahcisata0 port 3: PHY offline
ahcisata0 port 1: PHY offline
ahcisata0 port 2: PHY offline
...
wd0 at atabus0 drive 0
wd0: <WDC WD20EFRX-68EUZN0>
wd0: drive supports 16-sector PIO transfers, LBA48 addressing
wd0: 1863 GB, 3876021 cyl, 16 head, 63 sec, 512 bytes/sect x 3907029168 sectors (0 bytes/physsect; first aligned sector: 8)
wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133), NCQ (32 tags) w/PRIO
wd0(ahcisata0:0:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133) (using DMA), NCQ (31 tags) w/PRIO

I don't suppose this gives anyone any helpful thoughts?

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