* Re: [9fans] kprint
2001-10-01 14:09 [9fans] kprint rog
@ 2001-10-01 14:08 ` suspect
2001-10-01 14:16 ` William Josephson
1 sibling, 0 replies; 4+ messages in thread
From: suspect @ 2001-10-01 14:08 UTC (permalink / raw)
To: 9fans
The original iteration of the "console" window, now the "log" window did
something along those lines. I never figured why it was changed to
what it is now, or whether those changes were not directly merged.
-
On Mon, 1 Oct 2001 rog@vitanuova.com wrote:
>
> it's a fairly natural thing to do, i think. i've wanted to do something
> similar in inferno for a while. (^t^tp destroying the screen on a
> bitsy is annoying).
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [9fans] kprint
@ 2001-10-01 14:09 rog
2001-10-01 14:08 ` suspect
2001-10-01 14:16 ` William Josephson
0 siblings, 2 replies; 4+ messages in thread
From: rog @ 2001-10-01 14:09 UTC (permalink / raw)
To: 9fans
> A very pleasant addition which I just backported to 3rd Ed. this
> weekend. Quite convenient. Didn't realize it was Russ's idea, though.
it's a fairly natural thing to do, i think. i've wanted to do something
similar in inferno for a while. (^t^tp destroying the screen on a
bitsy is annoying).
some issues that i was wondering about:
o storage: do you have a circular buffer, or just accept an
ever-increasing buffer size ?
o blocking: does a process reading at the end of the file
block until the next kernel print message arrives or does it
look like a normal file which you have to poll (e.g. tail -f)?
o do you allow user processes to append messages themselves,
possibly a convenient place to put daemon log messages?
o multiplexing: do you allow several processes to access kprint
simultaneously?
rog.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [9fans] kprint
2001-10-01 14:09 [9fans] kprint rog
2001-10-01 14:08 ` suspect
@ 2001-10-01 14:16 ` William Josephson
1 sibling, 0 replies; 4+ messages in thread
From: William Josephson @ 2001-10-01 14:16 UTC (permalink / raw)
To: 9fans
On Mon, Oct 01, 2001 at 03:09:12PM +0100, rog@vitanuova.com wrote:
The following only apply to my backport, but:
> some issues that i was wondering about:
> o storage: do you have a circular buffer, or just accept an
> ever-increasing buffer size ?
I just use a Queue with an 8K limit. IIRC, that's what the new kernel
does, too.
> o blocking: does a process reading at the end of the file
> block until the next kernel print message arrives or does it
> look like a normal file which you have to poll (e.g. tail -f)?
Currently, the process blocks -- I just open a rio window and type
'cat /dev/kprint' and put the window in scroll mode (or not).
> o do you allow user processes to append messages themselves,
> possibly a convenient place to put daemon log messages?
One could, I suppose. I haven't thought about it, but it seems to me
that I'd want a more general logging facility that could write
messages to stable storage if I were doing that. It might be better
to separate the two and have log messages and kernel prints go
somewhere else for logging. At least as I use it, /dev/kprint is for
reading exceptional messages while I'm debugging so I don't hose rio.
> o multiplexing: do you allow several processes to access kprint
> simultaneously?
/dev/kprint is exclusive use. This is how it is in the new kernel, too.
At least in my case, it makes the implementation easier and I don't think
the added complexity would yield all that much benefit given how I use it.
-WJ
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [9fans] kprint
@ 2001-10-01 15:31 Russ Cox
0 siblings, 0 replies; 4+ messages in thread
From: Russ Cox @ 2001-10-01 15:31 UTC (permalink / raw)
To: 9fans
William is right on all counts.
I want to add:
o storage: do you have a circular buffer, or just accept an
ever-increasing buffer size ?
We use qnoblock(kprintoq, 1), which results in dropping
the tail of the log. It's an 8k log, so if someone is reading
I don't expect any drops.
o do you allow user processes to append messages themselves,
possibly a convenient place to put daemon log messages?
As Rob's man page excerpt pointed out, if you write to
#c/cons on a bitmapped terminal and /dev/kprint is open,
the output only goes to kprint. That seemed easier to explain
at the time. So syslog(1, ...) gets sent to kprint if in use.
Russ
^ permalink raw reply [flat|nested] 4+ messages in thread
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