Re: [RFC][PATCH] tracing/x86: Save CR2 before tracing irqsoff on error_entry

[Steven Rostedt]

On Thu, 21 Mar 2019 20:31:52 +0100
Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> > 
> > No I didn't. Some users only care about performance, but find memory
> > cheap.  
> 
> Because cache-misses are free?

If I ever did implement this, I would try to get all the data out of
line as much as possible, where only a nop would be inserted:

	jmp lockdep_code
	raw_locking
1:

[..]

lockdep_code:
	do all that lockdep needs
	raw_locking
	jmp 1b

and have that converted to:


	nop // jmp lockdep_code
	raw_locking
1:

when disabled. So the only extra pressure on the icache is the nop.

-- Steve