Messages in this thread | | | Date | Mon, 7 Mar 2022 20:37:59 +0700 | From | Ammar Faizi <> | Subject | Re: [PATCH v1 0/2] x86: Avoid using INC and DEC instructions on hot paths |
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On 3/7/22 7:38 PM, Borislav Petkov wrote: > On Mon, Mar 07, 2022 at 06:45:56PM +0700, Ammar Faizi wrote: >> In order to take maximum advantage of out-of-order execution, >> avoid using INC/DEC instructions when appropriate. INC/DEC only >> writes to part of the flags register, which can cause a partial >> flag register stall. This series replaces INC/DEC with ADD/SUB. > > "Improvements" like that need to show in benchmark runs - not > microbenchmark - that they bring anything. Just by looking at them, I'd > say they won't show any difference. But I'm always open to surprises.
OK, thanks for taking a look. I will play a bit more with this. Not sure how much the visible improvement. If I can win some numbers (probably can't), I will be back to this thread.
> Btw, you don't have to send all your patches directly to me - there are > other x86 maintainers. IOW, you can use scripts/get_maintainer.pl to > figure out who to send them to.
I did anyway, all CC list here I took from that script. I will try to give other maintainers a turn next time.
> Also, I'd advise going over Documentation/process/ if you're new to this. > Especially Documentation/process/submitting-patches.rst. I might've missed the benchmark backup part. Will review those documents again.
-- Ammar Faizi
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