From: Davidlohr Bueso <dave@stgolabs.net>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH 3/4] x86,asm: Re-work smp_store_mb()
Date: Mon, 2 Nov 2015 17:36:25 -0800 [thread overview]
Message-ID: <20151103013625.GD1707@linux-uzut.site> (raw)
In-Reply-To: <CA+55aFynbkeuUGs9s-q+fLY6MeRBA6MjEyWWbbe7A5AaqsAknw@mail.gmail.com>
On Mon, 02 Nov 2015, Linus Torvalds wrote:
>On Mon, Nov 2, 2015 at 12:15 PM, Davidlohr Bueso <dave@stgolabs.net> wrote:
>>
>> So I ran some experiments on an IvyBridge (2.8GHz) and the cost of XCHG is
>> constantly cheaper (by at least half the latency) than MFENCE. While there
>> was a decent amount of variation, this difference remained rather constant.
>
>Mind testing "lock addq $0,0(%rsp)" instead of mfence? That's what we
>use on old cpu's without one (ie 32-bit).
I'm getting results very close to xchg.
>I'm not actually convinced that mfence is necessarily a good idea. I
>could easily see it being microcode, for example.
Interesting.
>
>At least on my Haswell, the "lock addq" is pretty much exactly half
>the cost of "mfence".
Ok, his coincides with my results on IvB.
next prev parent reply other threads:[~2015-11-03 1:36 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-27 19:53 [PATCH -tip 0/4] A few updates around smp_store_mb() Davidlohr Bueso
2015-10-27 19:53 ` [PATCH 1/4] arch,cmpxchg: Remove tas() definitions Davidlohr Bueso
2015-10-27 23:27 ` David Howells
2015-12-04 12:01 ` [tip:locking/core] locking/cmpxchg, arch: " tip-bot for Davidlohr Bueso
2015-10-27 19:53 ` [PATCH 2/4] arch,barrier: Use smp barriers in smp_store_release() Davidlohr Bueso
2015-10-27 20:03 ` Davidlohr Bueso
2015-12-04 12:01 ` [tip:locking/core] lcoking/barriers, arch: " tip-bot for Davidlohr Bueso
2015-10-27 19:53 ` [PATCH 3/4] x86,asm: Re-work smp_store_mb() Davidlohr Bueso
2015-10-27 21:33 ` Linus Torvalds
2015-10-27 22:01 ` Davidlohr Bueso
2015-10-27 22:37 ` Peter Zijlstra
2015-10-28 19:49 ` Davidlohr Bueso
2015-11-02 20:15 ` Davidlohr Bueso
2015-11-03 0:06 ` Linus Torvalds
2015-11-03 1:36 ` Davidlohr Bueso [this message]
2016-01-12 13:57 ` Michael S. Tsirkin
2016-01-12 13:57 ` Michael S. Tsirkin
2016-01-12 17:20 ` Linus Torvalds
2016-01-12 17:20 ` Linus Torvalds
2016-01-12 17:45 ` Michael S. Tsirkin
2016-01-12 17:45 ` Michael S. Tsirkin
2016-01-12 18:04 ` Linus Torvalds
2016-01-12 18:04 ` Linus Torvalds
2016-01-12 20:30 ` Andy Lutomirski
2016-01-12 20:54 ` Linus Torvalds
2016-01-12 20:54 ` Linus Torvalds
2016-01-12 20:59 ` Andy Lutomirski
2016-01-12 20:59 ` Andy Lutomirski
2016-01-12 21:37 ` Linus Torvalds
2016-01-12 21:37 ` Linus Torvalds
2016-01-12 22:14 ` Michael S. Tsirkin
2016-01-12 22:14 ` Michael S. Tsirkin
2016-01-13 16:20 ` Michael S. Tsirkin
2016-01-13 16:20 ` Michael S. Tsirkin
2016-01-12 22:21 ` Michael S. Tsirkin
2016-01-12 22:21 ` Michael S. Tsirkin
2016-01-12 22:55 ` H. Peter Anvin
2016-01-12 22:55 ` H. Peter Anvin
2016-01-12 23:24 ` Linus Torvalds
2016-01-12 23:24 ` Linus Torvalds
2016-01-13 16:17 ` Borislav Petkov
2016-01-13 16:17 ` Borislav Petkov
2016-01-13 16:25 ` Michael S. Tsirkin
2016-01-13 16:25 ` Michael S. Tsirkin
2016-01-13 16:33 ` Borislav Petkov
2016-01-13 16:33 ` Borislav Petkov
2016-01-13 16:42 ` Michael S. Tsirkin
2016-01-13 16:42 ` Michael S. Tsirkin
2016-01-13 16:53 ` Borislav Petkov
2016-01-13 16:53 ` Borislav Petkov
2016-01-13 17:00 ` Michael S. Tsirkin
2016-01-13 17:00 ` Michael S. Tsirkin
2016-01-13 18:38 ` Linus Torvalds
2016-01-13 18:38 ` Linus Torvalds
2015-10-27 19:53 ` [PATCH 4/4] doc,smp: Remove ambiguous statement in smp_store_mb() Davidlohr Bueso
2015-12-04 12:01 ` [tip:locking/core] locking/barriers, arch: Remove ambiguous statement in the smp_store_mb() documentation tip-bot for Davidlohr Bueso
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=20151103013625.GD1707@linux-uzut.site \
--to=dave@stgolabs.net \
--cc=dbueso@suse.de \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.