Re: [PATCH] Improve spinlock inline assembly for x86.

On Mon, Jan 18, 2016 at 2:14 PM, Kevin Grittner <kgrittn(at)gmail(dot)com> wrote:
>> You get just as much churn by changing code elsewhere, which
>> often causes code movement and alignment changes.
>
> It's hard to understand quite what you're saying there. If you're
> saying that code changes that should be performance neutral can
> sometimes affect performance because of alignment of code with
> cache line boundaries -- I absolutely agree; is that an argument
> against performance testing performance patches?

No, it isn't an argument against performance testing patches like
this, but I don't think anyone suggested otherwise. Of course every
performance related patch should be tested to make sure it meets its
goals and at acceptable cost, but I don't think that Andreas' patch is
necessarily a performance patch. There can be value in removing
superfluous code; doing so sometimes clarifies intent and
understanding.

--
Peter Geoghegan