From: Leonardo Bras <leobras.c@gmail.com>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: Leonardo Bras <leobras.c@gmail.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Michal Hocko <mhocko@suse.com>,
linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
linux-mm@kvack.org, Johannes Weiner <hannes@cmpxchg.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Shakeel Butt <shakeel.butt@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Hyeonggon Yoo <42.hyeyoo@gmail.com>,
Leonardo Bras <leobras@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Waiman Long <longman@redhat.com>,
Boqun Feng <boqun.feng@gmail.com>,
Frederic Weisbecker <fweisbecker@suse.de>
Subject: Re: [PATCH 0/4] Introduce QPW for per-cpu operations
Date: Tue, 10 Mar 2026 21:01:00 -0300 [thread overview]
Message-ID: <abCwvB36SLGC_7Yg@WindFlash> (raw)
In-Reply-To: <cbd42744-31e1-439c-b0f0-0cad052d3d9b@kernel.org>
On Mon, Mar 09, 2026 at 10:52:55AM +0100, Vlastimil Babka (SUSE) wrote:
> On 3/8/26 18:41, Leonardo Bras wrote:
> > Hi Marcelo,
> >
> > Great, hiding migrate_disable under the static branch is the best scenario.
> >
> > I wonder why we spend 2 cycles on the static branches, though, should be
> > close to nothing unless the branch predictor is too busy already. Well, we
>
> AFAIK static branches are runtime patched to non-conditional jumps or nops,
> so there's nothing left for the branch predictor to do. Or maybe I
> misunderstand your comment.
> It does however increase code footprint and thus instruction cache usage, so
> maybe that's an effect of that.
Oh, I was not aware of that part. Since we can actually change the the
branch decision variable in runtime, I guessed that it was just a optimized
way for the processor to use the branch predictor.
If it makes a non-conditional branch is even better then.
Thanks!
Leo
>
> > can always try to optimize in a different way.
> >
> > Thanks for the effort on this!
> > Leo
next prev parent reply other threads:[~2026-03-11 0:01 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-06 14:34 [PATCH 0/4] Introduce QPW for per-cpu operations Marcelo Tosatti
2026-02-06 14:34 ` [PATCH 1/4] Introducing qpw_lock() and per-cpu queue & flush work Marcelo Tosatti
2026-02-06 15:20 ` Marcelo Tosatti
2026-02-07 0:16 ` Leonardo Bras
2026-02-11 12:09 ` Marcelo Tosatti
2026-02-14 21:32 ` Leonardo Bras
2026-02-06 14:34 ` [PATCH 2/4] mm/swap: move bh draining into a separate workqueue Marcelo Tosatti
2026-02-06 14:34 ` [PATCH 3/4] swap: apply new queue_percpu_work_on() interface Marcelo Tosatti
2026-02-07 1:06 ` Leonardo Bras
2026-02-26 15:49 ` Marcelo Tosatti
2026-03-08 17:35 ` Leonardo Bras
2026-02-06 14:34 ` [PATCH 4/4] slub: " Marcelo Tosatti
2026-02-07 1:27 ` Leonardo Bras
2026-02-06 23:56 ` [PATCH 0/4] Introduce QPW for per-cpu operations Leonardo Bras
2026-02-10 14:01 ` Michal Hocko
2026-02-11 12:01 ` Marcelo Tosatti
2026-02-11 12:11 ` Marcelo Tosatti
2026-02-14 21:35 ` Leonardo Bras
2026-02-11 16:38 ` Michal Hocko
2026-02-11 16:50 ` Marcelo Tosatti
2026-02-11 16:59 ` Vlastimil Babka
2026-02-11 17:07 ` Michal Hocko
2026-02-14 22:02 ` Leonardo Bras
2026-02-16 11:00 ` Michal Hocko
2026-02-19 15:27 ` Marcelo Tosatti
2026-02-19 19:30 ` Michal Hocko
2026-02-20 14:30 ` Marcelo Tosatti
2026-02-23 9:18 ` Michal Hocko
2026-03-03 10:55 ` Frederic Weisbecker
2026-02-23 21:56 ` Frederic Weisbecker
2026-02-24 17:23 ` Marcelo Tosatti
2026-02-25 21:49 ` Frederic Weisbecker
2026-02-26 7:06 ` Michal Hocko
2026-02-26 11:41 ` Marcelo Tosatti
2026-03-03 11:08 ` Frederic Weisbecker
2026-02-20 10:48 ` Vlastimil Babka
2026-02-20 12:31 ` Michal Hocko
2026-02-20 17:35 ` Marcelo Tosatti
2026-02-20 17:58 ` Vlastimil Babka
2026-02-20 19:01 ` Marcelo Tosatti
2026-02-23 9:11 ` Michal Hocko
2026-02-23 11:20 ` Marcelo Tosatti
2026-02-24 14:40 ` Frederic Weisbecker
2026-02-24 18:12 ` Marcelo Tosatti
2026-02-20 16:51 ` Marcelo Tosatti
2026-02-20 16:55 ` Marcelo Tosatti
2026-02-20 22:38 ` Leonardo Bras
2026-02-23 18:09 ` Vlastimil Babka
2026-02-26 18:24 ` Marcelo Tosatti
2026-02-20 21:58 ` Leonardo Bras
2026-02-23 9:06 ` Michal Hocko
2026-02-28 1:23 ` Leonardo Bras
2026-03-03 0:19 ` Marcelo Tosatti
2026-03-08 17:41 ` Leonardo Bras
2026-03-09 9:52 ` Vlastimil Babka (SUSE)
2026-03-11 0:01 ` Leonardo Bras [this message]
2026-03-10 21:24 ` Marcelo Tosatti
2026-03-11 0:03 ` Leonardo Bras
2026-03-11 10:23 ` Marcelo Tosatti
2026-02-19 13:15 ` Marcelo Tosatti
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