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Date:      Wed, 30 Jan 2019 17:18:45 -0800
From:      Mark Millard <marklmi@yahoo.com>
To:        FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>
Subject:   Re: PoerMac G5 "4 core" (system total): some from-power-off booting observations of the modern VM_MAX_KERNEL_ADDRESS value mixed with usefdt=1
Message-ID:  <FA03DF6B-B8FC-42E5-A5B3-2891D88BDAD7@yahoo.com>
In-Reply-To: <2153561F-FE12-4BA0-9856-F75110401AB6@yahoo.com>
References:  <2153561F-FE12-4BA0-9856-F75110401AB6@yahoo.com>

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[Where boot -v output is different between booting to completion vs.
hanging up: actual text.]

On 2019-Jan-29, at 17:52, Mark Millard <marklmi at yahoo.com> wrote:

> For the modern VM_MAX_KERNEL_ADDRESS value and also use of the =
usefdt=3D1 case:
>=20
> This usually hang during boot during the "Waking up CPU" message =
sequence.
>=20
> But not always. Powering off and retrying , sometimes just a few =
times, and
> other times dozens of times, the system that I have access to does =
eventually
> boot for the combination. So some sort of race condition or lack of =
stable
> initialization?
>=20
> When it does boot, smp seems to be set up and working.
>=20
> Once booted, it is usually not very long until the fans are going =
wild,
> other than an occasional, temporary lull.
>=20
>=20
>=20
> For for shutting down the following applies to both =
VM_MAX_KERNEL_ADDRESS
> values when a usefdt=3D1 type of context is in use:
>=20
> When I've kept explicit track, I've not had any example of all of the:
>=20
> Waiting (max 60 seconds) for system thread `bufdaemon' to stop...
> Waiting (max 60 seconds) for system thread `bufspacedaemon-1' to =
stop...
> Waiting (max 60 seconds) for system thread `bufspacedaemon-0' to =
stop...
> . . .
>=20
> getting to "done": instead one or more time out. Which and how many
> vary.
>=20
> The fans tend to take off for both VM_MAX_KERNEL_ADDRESS values. The
> buf*daemon timeouts happen even if the fans have not taken off.
>=20

With VM_MAX_KERNEL_ADDRESS reverted or a successful
boot with the modern value:

Adding CPU 0, hwref=3Dcd38, awake=3D1
Waking up CPU 3 (dev=3Dc480)
Adding CPU 3, hwref=3Dc480, awake=3D1
Waking up CPU 2 (dev=3Dc768)
Adding CPU 2, hwref=3Dc768, awake=3D1
Waking up CPU 1 (dev=3Dca50)
Adding CPU 1, hwref=3Dca50, awake=3D1
SMP: AP CPU #3 launched
SMP: AP CPU #2 launched
SMP: AP CPU #1 launched
Trying to mount root from ufs:/dev/ufs/FBSDG5L2rootfs [rw,noatime]...


With the modern VM_MAX_KERNEL_ADDRESS value for a boot attempt
that failed, an example (typed from a picture of the screen) is:

Adding CPU 0, hwref=3Dcd38, awake=3D1
Waking up CPU 3 (dev=3Dc480)

Another is:

Adding CPU 0, hwref=3Dcd38, awake=3D1
Waking up CPU 3 (dev=3Dc480)
Waking up CPU 2 (dev=3Dc768)

(Both examples have no more output.)

So CPUs 1..3 do not get "Adding CPU" messages. Also:
I do not remember seeing all 3 "Waking up CPU" messages,
just 1 or 2 of them.

(Sometimes the "Trying to mount root from" message is in
the mix as I remember.)


One point of difference that is consistently observable for
the old vs. modern VM_MAX_KERNEL_ADDRESS values is how many
bufspacedaemon-* threads there are:

old VM_MAX_KERNEL_ADDRESS value: 0..2
new VM_MAX_KERNEL_ADDRESS value: 0..6


I have had many boot attempts in a row boot
for the modern VM_MAX_KERNEL_ADDRESS value,
though not as many as the dozens of failures
in a row. Highly variable with lots of
testing.

=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)




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