Re: [PATCH v3] printk: add option to print cpu id

On Fri, Aug 3, 2012 at 10:54 AM, Andi Kleen [off-list ref] wrote:

Vikram Pandita [off-list ref] writes:

quoted

From: Vikram Pandita <redacted>

Introduce config option to enable CPU id reporting for printk() calls.

What's wrong with using trace_printk for this?

trace_printk works only when you know the _exact_ path in code that
you want to profile.
When you have no idea of a random lockup, then it would be kind of
touch and time consuming
to put trace prints all around the code.

That's much faster
anyways. Generally printk is so slow that it's typically useless for
instrumenting races.

As stated in another thread, its found useful to debug some specific cases:
Check thread: http://marc.info/?l=linux-omap&m=134401269106619&w=2

And really: Wasting 1/3 of the 80 character line is too much.

You _WASTE_ 4 chars only if you are interested in this info by
enabling: CONFIG_PRINTK_CPUID
Just like you _WASTE_ 15 chars when you enable existing: CONFIG_PRINTK_TIME

For general usecase, recommendation would be to keep these options disabled.
Working on shipping products, i find almost all shipping with
CONFIG_PRINTK_TIME enabled, so there must be some value.
Same would hold for the use case being debugged for CPUID enabling.

-Andi

--
ak@linux.intel.com -- Speaking for myself only