[PATCH 3/6] pstore: Add persistent function tracing

[Colin Cross]

On Fri, Jun 15, 2012 at 3:00 PM, Luck, Tony <tony.luck at intel.com> wrote:
>> With function tracing the impact to performance is tremendous. Just
>> recording two long words is a 130% hit to performance. Now multiply that
>> to recording strings.
>
> If pstore is writing to a flash based backend - then there will be many
> milli-seconds of delay. I think the time taken to convert from binary to
> ascii would be insignificant.

Function tracing into flash would be silly, adding milliseconds of
overhead to every function call is enormous.  The normal use case for
this is tracing to persistent ram, and even the difference between 2
and 3 words in the binary format was noticeable.  Converting to ascii
would expand 2 words to at least 20 words, making the entire feature
useless.