On 7/23/20 2:47 PM, peterz@infradead.org wrote:

On Thu, Jul 23, 2020 at 02:32:36PM -0400, Waiman Long wrote:

quoted

BTW, do you have any comment on my v2 lock holder cpu info qspinlock patch?
I will have to update the patch to fix the reported 0-day test problem, but
I want to collect other feedback before sending out v3.

I want to say I hate it all, it adds instructions to a path we spend an
aweful lot of time optimizing without really getting anything back for
it.

It does add some extra instruction that may slow it down slightly, but I 
don't agree that it gives nothing back. The cpu lock holder information 
can be useful in analyzing crash dumps and in some debugging situation. 
I think it can be useful in RHEL for this readon. How about an x86 
config option to allow distros to decide if they want to have it 
enabled? I will make sure that it will have no performance degradation 
if the option is not enabled.

Cheers,
Longman