Re: perf_fuzzer compiled for x32 causes reboot

[Steven Rostedt]

On Fri, 28 Feb 2014 21:56:38 +0100
Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:


> Like already said; _trace is an absolutely abysmal name. Also you
> _really_ don't want an unconditional CR2 write in there, that's just
> stupidly expensive.

But a read isn't. Which is why we only do a write if the copy caused a
page fault (which is already expensive).

The proposed patch will have:

	if (cr2 != read_cr2())
		write_cr2(cr2);

> 
> Also, this function is called a _LOT_ under certain workloads, I don't
> know how cheap a CR2 read is, but it had better be really cheap.

That's a HPA question.

-- Steve
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/