20 Sep
2024
20 Sep
'24
1:10 a.m.
From: Ron Minnich
Ed got tired of watching the bootstrap slowness
This may be a dumb question (in which case, my apologies), but which part of
booting a PDP-11 UNIX was slow? And thus, which parts did he bypass in a
'quick reboot'? (I'm having a bit of a hard time working it out.) I can
think
of the following stages as potentially being 'slow':
1 - reading in the kernel image from disk
2 - sizing/clearing main memory
3 - loading running /etc/init
3A - creating all the 'loqin's
3B - starting all the daemons/etc with /etc/rc
(There's obviously a conflict between 2 and 3*; one can't avoid 3* if one
does 2.)
Which ones did he want to avoid?
Avoiding 3* puts some limitations on the system, obviously, because it means
one has to keep running processes around; the process table has to have the
same format (and be in the same location - or it has to be moved before the
new system is started). (Technically, I guess one would have to save the
inode and file tables, too; there isn't enough saved data in the kernel to
re-open files, plus there are file read/write ocation pointers, etc.)
One could sort of do 2 also, if one were prepared to 1) swap all processes
out to secondary storage before 'rebooting', and ii) saving the process table.
But I'm wondering: is Ed's work in 1977 the
first "kernel boots kernel"
or was there something before?
Are you talking about for UNIX, or across all operating systems? I don't have
that broad a memory any more, to know - did TWENEX have something like that?
Noel
20 Sep
20 Sep
1:42 a.m.
New subject: kernel boots kernel in 1977
It's been too long. Plus, for all I know, it may have been a "wouldn't
this
be cool" project that did not work out. I don't recall that we ended up
using it much. But that was almost 50 years ago, so your guess is as good
as mine.
It was for sure a cute hack.
On Thu, Sep 19, 2024 at 12:10 PM Noel Chiappa <jnc(a)mercury.lcs.mit.edu>
wrote:
From: Ron
Minnich
Ed got tired of watching the bootstrap slowness
This may be a dumb question (in which case, my apologies), but which part
of
booting a PDP-11 UNIX was slow? And thus, which parts did he bypass in a
'quick reboot'? (I'm having a bit of a hard time working it out.) I can
think
of the following stages as potentially being 'slow':
1 - reading in the kernel image from disk
2 - sizing/clearing main memory
3 - loading running /etc/init
3A - creating all the 'loqin's
3B - starting all the daemons/etc with /etc/rc
(There's obviously a conflict between 2 and 3*; one can't avoid 3* if one
does 2.)
Which ones did he want to avoid?
Avoiding 3* puts some limitations on the system, obviously, because it
means
one has to keep running processes around; the process table has to have the
same format (and be in the same location - or it has to be moved before the
new system is started). (Technically, I guess one would have to save the
inode and file tables, too; there isn't enough saved data in the kernel to
re-open files, plus there are file read/write ocation pointers, etc.)
One could sort of do 2 also, if one were prepared to 1) swap all processes
out to secondary storage before 'rebooting', and ii) saving the process
table.
But I'm wondering: is Ed's work in 1977
the first "kernel boots
kernel"
or was there something before?
Are you talking about for UNIX, or across all operating systems? I don't
have
that broad a memory any more, to know - did TWENEX have something like
that?
Noel
21 Sep
21 Sep
1:47 a.m.
New subject: kernel boots kernel in 1977
I can see an immedaite advantage in
1 - reading in the kernel image from disk
As late as August of 1983, as that's the last time I had to do it, there were still
systems in operation that you had to manually input the boot loader by hand using front
panel switches.
See https://gunkies.org/wiki/PDP-11_Bootstrap_Loader
-Brian
ron minnich rminnich at gmail.com
Fri Sep 20 05:42:45 AEST 2024
It's been too long. Plus, for all I know, it may have been a "wouldn't
this
be cool" project that did not work out. I don't recall that we ended up
using it much. But that was almost 50 years ago, so your guess is as good
as mine.
It was for sure a cute hack.
On Thu, Sep 19, 2024 at 12:10b/PM Noel Chiappa <jnc at mercury.lcs.mit.edu>
wrote:
> > From: Ron Minnich
>
> > Ed got tired of watching the bootstrap slowness
>
> This may be a dumb question (in which case, my apologies), but which part
> of
> booting a PDP-11 UNIX was slow? And thus, which parts did he bypass in a
> 'quick reboot'? (I'm having a bit of a hard time working it out.) I
can
> think
> of the following stages as potentially being 'slow':
>
> 1 - reading in the kernel image from disk
> 2 - sizing/clearing main memory
> 3 - loading running /etc/init
> 3A - creating all the 'loqin's
> 3B - starting all the daemons/etc with /etc/rc
>
> (There's obviously a conflict between 2 and 3*; one can't avoid 3* if one
> does 2.)
>
> Which ones did he want to avoid?
>
> Avoiding 3* puts some limitations on the system, obviously, because it
> means
> one has to keep running processes around; the process table has to have the
> same format (and be in the same location - or it has to be moved before the
> new system is started). (Technically, I guess one would have to save the
> inode and file tables, too; there isn't enough saved data in the kernel to
> re-open files, plus there are file read/write ocation pointers, etc.)
>
> One could sort of do 2 also, if one were prepared to 1) swap all processes
> out to secondary storage before 'rebooting', and ii) saving the process
> table.
>
> > But I'm wondering: is Ed's work in 1977 the first "kernel
boots
> kernel"
> > or was there something before?
>
> Are you talking about for UNIX, or across all operating systems? I don't
> have
> that broad a memory any more, to know - did TWENEX have something like
> that?
>
> Noel
93
days inactive
94
days old
2 comments
3 participants
participants (3)
-
Brian Walden -
jnc＠mercury.lcs.mit.edu -
ron minnich