Re: CONFIG_PRINTK_TIME woes

David S. Miller
2005-08-22T20:42:33Z

From: Jason Uhlenkott <jasonuhl@sgi.com>
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 really significant? I strongly
> suspect that the overhead of printk() is high enough, even when we're
> just spewing to the dmesg buffer and not the console, that we have a
> lot more precision than accuracy at nanosecond resolution.

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.

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 :-)