From: Marcelo Tosatti <mtosatti@redhat.com>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.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.c@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Waiman Long <longman@redhat.com>,
Boqun Feun <boqun.feng@gmail.com>,
Frederic Weisbecker <frederic@kernel.org>
Subject: Re: [PATCH v2 2/5] Introducing qpw_lock() and per-cpu queue & flush work
Date: Tue, 3 Mar 2026 13:02:13 -0300 [thread overview]
Message-ID: <aacGBc9x+zn1tluU@tpad> (raw)
In-Reply-To: <682380ba-c8f3-4023-928c-2152e934f8db@kernel.org>
On Tue, Mar 03, 2026 at 01:03:36PM +0100, Vlastimil Babka (SUSE) wrote:
> On 3/2/26 16:49, Marcelo Tosatti wrote:
> > +#define local_qpw_lock(lock) \
> > + do { \
> > + if (static_branch_maybe(CONFIG_QPW_DEFAULT, &qpw_sl)) { \
> > + migrate_disable(); \
>
> Have you considered using migrate_disable() on PREEMPT_RT and
> preempt_disable() on !PREEMPT_RT since it's cheaper? It's what the pcp
> locking in mm/page_alloc.c does, for that reason. It should reduce the
> overhead with qpw=1 on !PREEMPT_RT.
migrate_disable:
Patched kernel, CONFIG_QPW=y, qpw=1: 192 cycles
preempt_disable:
[ 65.497223] kmalloc_bench: Avg cycles per kmalloc: 184 cycles
I tried it before, but it was crashing for some reason which i didnt
look into (perhaps PREEMPT_RT was enabled).
Will change this for the next iteration, thanks.
next prev parent reply other threads:[~2026-03-06 1:48 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-02 15:49 [PATCH v2 0/5] Introduce QPW for per-cpu operations (v2) Marcelo Tosatti
2026-03-02 15:49 ` [PATCH v2 1/5] slab: distinguish lock and trylock for sheaf_flush_main() Marcelo Tosatti
2026-03-02 15:49 ` [PATCH v2 2/5] Introducing qpw_lock() and per-cpu queue & flush work Marcelo Tosatti
2026-03-03 12:03 ` Vlastimil Babka (SUSE)
2026-03-03 16:02 ` Marcelo Tosatti [this message]
2026-03-02 15:49 ` [PATCH v2 3/5] mm/swap: move bh draining into a separate workqueue Marcelo Tosatti
2026-03-02 15:49 ` [PATCH v2 4/5] swap: apply new queue_percpu_work_on() interface Marcelo Tosatti
2026-03-02 15:49 ` [PATCH v2 5/5] slub: " Marcelo Tosatti
2026-03-03 11:15 ` [PATCH v2 0/5] Introduce QPW for per-cpu operations (v2) Frederic Weisbecker
2026-03-03 12:07 ` Vlastimil Babka (SUSE)
2026-03-05 16:55 ` Frederic Weisbecker
2026-03-06 1:47 ` Marcelo Tosatti
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