Andrew Morton wrote:
> Andrew Morton <[EMAIL PROTECTED]> wrote:
>
>>How about we give each arch a printk_clock()?
>
>
> Which might be as simple as this..
>
>
> --- devel/kernel/printk.c~printk_clock2005-08-21 02:14:05.0
> -0700
> +++ devel-akpm/kernel/printk.c2005-08-2
Andrew Morton wrote:
> Nick Piggin <[EMAIL PROTECTED]> wrote:
>>
>>What about just using jiffies, then?
>>
>>Really, sched_clock() is very broken for this (I know you're
>>not arguing against that).
>>
>>It can go backwards when called twice from the same CPU, and the
>>number returned by one CPU n
David S. Miller wrote:
This is a useful feature, please do not labotomize it just because
it's difficult to implement on ia64. Just make a
"printk_get_timestamp_because_ia64_sucks()" interface or something
like that :-)
I was a bit unclear when I raised this issue. It is not just an
ia64 prob
>I'd hate to have to test for something for CONFIG_PRINTK_TIME
>every time sched_clock() is being called.
Me too.
>The quick fix would seem to be to only allow CONFIG_PRINTK_TIME
>from kernel cmdline to make it happen a bit later. So basically
>make int printk_time = 0 until command line is evalu
* Andrew Morton <[EMAIL PROTECTED]> [050821 02:15]:
> "Luck, Tony" <[EMAIL PROTECTED]> wrote:
> >
> > It has been pointed out to me that ia64 doesn't boot
> > with CONFIG_PRINTK_TIME=y. The issue is the call to
> > sched_clock() ... which on ia64 accesses some per-cpu
> > data to adjust for possib
[EMAIL PROTECTED] writes:
> Earlier I said that it would be possible to provide a simplified
> do_gettimeofday() call that met the no locks requirement. I still
> think this is possible, but most architectures would only get
> jiffie resolution from this (only ia64, sparc64 and HPET users
> have
>Ah, thanks. Presumably it'll be considerably longer with %d's and %s's in
>there. But still, ~10 usecs is good resolution for I/O operations.
The variation in times from one call to the next seems to be
greater than the time to evaluate 4 "%d" arguments.
So we are back to how to get a timestam
>How fast is printk? I haven't looked.
>
>ie: if you do back-to-back printk's, what's the timestamp increment?
On ia64 it looks like about 4-5 usec increment for back-to-back
printk (with no serial console configured, and dmesg -n to turn
off messages to the VGA console).
-Tony
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[EMAIL PROTECTED] wrote:
>
> >How fast is printk? I haven't looked.
> >
> >ie: if you do back-to-back printk's, what's the timestamp increment?
>
> On ia64 it looks like about 4-5 usec increment for back-to-back
> printk (with no serial console configured, and dmesg -n to turn
> off messages to t
>I turn off VC logging, and I turn off disk sync'ing, so it goes
>straight to the page cache.
>
>I really do need sub-microsecond timings when I put a lot of
>printk tracing into the stack.
Right now you only have microsecond timing. Although printk() gets
"nanosecond" resolution from sched_clock(
"David S. Miller" <[EMAIL PROTECTED]> wrote:
>
> I really do need sub-microsecond timings when I put a lot of
> printk tracing into the stack.
How fast is printk? I haven't looked.
ie: if you do back-to-back printk's, what's the timestamp increment?
-
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>> we go there ... I'd like to hear whether there are usage models that
>> really need better resolution than jiffies can provide?
>
>I think so. Say you're debugging or performance tuning filesystem requests
>and I/O completions, etc. You disable the console with `dmesg -n', run the
>test then
From: Jason Uhlenkott <[EMAIL PROTECTED]>
Date: Mon, 22 Aug 2005 13:33:06 -0700
> On Mon, Aug 22, 2005 at 01:20:52PM -0700, David S. Miller wrote:
> > Not really, when I'm debugging TCP events over gigabit
> > these timestamps are exceptionally handy.
>
> Yes, but how many of those figures are re
On Mon, Aug 22, 2005 at 01:20:52PM -0700, David S. Miller wrote:
> From: [EMAIL PROTECTED]
> Date: Mon, 22 Aug 2005 10:42:22 -0700
>
> > At the other extreme ... the current use of sched_clock() with
> > potentially nano-second resolution is way over the top.
>
> Not really, when I'm debugging TC
From: [EMAIL PROTECTED]
Date: Mon, 22 Aug 2005 10:42:22 -0700
> At the other extreme ... the current use of sched_clock() with
> potentially nano-second resolution is way over the top.
Not really, when I'm debugging TCP events over gigabit
these timestamps are exceptionally handy.
-
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[EMAIL PROTECTED] wrote:
>
> At the other extreme ... the current use of sched_clock() with
> potentially nano-second resolution is way over the top. Logging
> to a serial console at 115200 a typical line from printk will take
> 2-4 milli-seconds to print ... so there would seem to be little
>
Andrew Morton wrote:
>jiffies wouldn't have sufficient resolution for this application. Bear in
>mind that this is just a debugging thing - it's better to have good
>resolution with occasional theoretical weirdness than to have poor
>resolution plus super-consistency, IMO.
The majority of archite
Nick Piggin <[EMAIL PROTECTED]> wrote:
>
> Andrew Morton wrote:
>
> >
> > yup.
> >
> >
> >>Why not use something like do_gettimeofday? (or I'm sure one
> >>of our time keepers can suggest the right thing to use).
> >
> >
> > do_gettimeofday() takes locks, so a) we can't do printk from inside
Andrew Morton wrote:
yup.
Why not use something like do_gettimeofday? (or I'm sure one
of our time keepers can suggest the right thing to use).
do_gettimeofday() takes locks, so a) we can't do printk from inside it and
Dang, yeah maybe this is the showstopper.
b) if you do a printk-fr
Nick Piggin <[EMAIL PROTECTED]> wrote:
>
> Andrew Morton wrote:
> > Andrew Morton <[EMAIL PROTECTED]> wrote:
> >
> >>How about we give each arch a printk_clock()?
> >
> >
> > Which might be as simple as this..
> >
> >
>
> sched_clock() shouldn't really be taken outside kernel/sched.c,
> espec
Andrew Morton wrote:
Andrew Morton <[EMAIL PROTECTED]> wrote:
How about we give each arch a printk_clock()?
Which might be as simple as this..
sched_clock() shouldn't really be taken outside kernel/sched.c,
especially for things like this.
It actually has some fundamental problems even
Andrew Morton <[EMAIL PROTECTED]> wrote:
>
> How about we give each arch a printk_clock()?
Which might be as simple as this..
--- devel/kernel/printk.c~printk_clock 2005-08-21 02:14:05.0 -0700
+++ devel-akpm/kernel/printk.c 2005-08-21 02:15:14.0 -0700
@@ -488,6 +488,11 @@ stati
"Luck, Tony" <[EMAIL PROTECTED]> wrote:
>
> It has been pointed out to me that ia64 doesn't boot
> with CONFIG_PRINTK_TIME=y. The issue is the call to
> sched_clock() ... which on ia64 accesses some per-cpu
> data to adjust for possible variations in processor
> speed between different cpus. Sinc
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