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SubjectRe: [RFC][PATCH] tracing/x86: Save CR2 before tracing irqsoff on error_entry
On Thu, 21 Mar 2019 20:31:52 +0100
Peter Zijlstra <peterz@infradead.org> 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



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