Messages in this thread | | | Date | Thu, 7 Sep 2017 09:04:46 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC 00/17] Pile o' entry stack changes |
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* Andy Lutomirski <luto@kernel.org> wrote:
> On Wed, Sep 6, 2017 at 3:16 PM, Andi Kleen <andi@firstfloor.org> wrote: > > Andy Lutomirski <luto@kernel.org> writes: > >> > >> - Lots of people (Linus included) have asked to convert the entry > >> code to pop registers on exit instead of movqing them off the > >> stack. This makes a bunch of progress in that direction. > > > > You should benchmark it on Atoms. Likely it's a regression there > > because they don't have the special PUSH/POP acceleration. > > I'm not entirely sure this is a worthwhile reason. Atom will lose a > few cycles due to POP throughput, but there's a lot less decode > bandwidth needed and we save a cache line or two.
I think we can also safely assume that Atom will eventually either join the 21st century or die out - mild Atom micro-costs are not a good reason to complicate the entry code...
Thanks,
Ingo
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