From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Juergen Gross <jgross@suse.com>,
Kees Cook <keescook@chromium.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Tony Luck <tony.luck@intel.com>,
Youquan Song <youquan.song@intel.com>,
linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org,
gwml@vger.gnuweeb.org, x86@kernel.org
Subject: Re: [PATCH v1 0/2] x86: Avoid using INC and DEC instructions on hot paths
Date: Mon, 7 Mar 2022 20:37:59 +0700 [thread overview]
Message-ID: <11dec988-0b4f-00f2-6fa6-8d08be95d106@gnuweeb.org> (raw)
In-Reply-To: <YiX81kD/668UdFBr@nazgul.tnic>
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
next prev parent reply other threads:[~2022-03-07 13:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-07 11:45 [PATCH v1 0/2] x86: Avoid using INC and DEC instructions on hot paths Ammar Faizi
2022-03-07 11:45 ` [PATCH v1 1/2] x86/include/asm: " Ammar Faizi
2022-03-07 11:45 ` [PATCH v1 2/2] x86/lib: " Ammar Faizi
2022-03-07 12:38 ` [PATCH v1 0/2] x86: " Borislav Petkov
2022-03-07 13:37 ` Ammar Faizi [this message]
2022-03-09 9:33 ` Borislav Petkov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=11dec988-0b4f-00f2-6fa6-8d08be95d106@gnuweeb.org \
--to=ammarfaizi2@gnuweeb.org \
--cc=andriy.shevchenko@linux.intel.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=gwml@vger.gnuweeb.org \
--cc=hpa@zytor.com \
--cc=jgross@suse.com \
--cc=jpoimboe@redhat.com \
--cc=keescook@chromium.org \
--cc=linux-hardening@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.com \
--cc=x86@kernel.org \
--cc=youquan.song@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).