From: Davidlohr Bueso <dave@stgolabs.net>
To: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Jesper Dangaard Brouer <brouer@redhat.com>,
rostedt@goodmis.org, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 1/2] mm/slub: optimize alloc/free fastpath by removing preemption on/off
Date: Mon, 05 Jan 2015 19:03:12 -0800 [thread overview]
Message-ID: <1420513392.24290.2.camel@stgolabs.net> (raw)
In-Reply-To: <1420421765-3209-1-git-send-email-iamjoonsoo.kim@lge.com>
On Mon, 2015-01-05 at 10:36 +0900, Joonsoo Kim wrote:
> - preempt_disable();
> - c = this_cpu_ptr(s->cpu_slab);
> + do {
> + tid = this_cpu_read(s->cpu_slab->tid);
> + c = this_cpu_ptr(s->cpu_slab);
> + } while (IS_ENABLED(CONFIG_PREEMPT) && unlikely(tid != c->tid));
> + barrier();
I don't see the compiler reodering the object/page stores below, since c
is updated in the loop anyway. Is this really necessary (same goes for
slab_free)? The generated code by gcc 4.8 looks correct without it.
Additionally, the implied barriers for preemption control aren't really
the same semantics used here (if that is actually the reason why you are
using them).
Thanks,
Davidlohr
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next prev parent reply other threads:[~2015-01-06 3:03 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-05 1:36 [PATCH 1/2] mm/slub: optimize alloc/free fastpath by removing preemption on/off Joonsoo Kim
2015-01-05 1:36 ` [PATCH 2/2] mm: don't use compound_head() in virt_to_head_page() Joonsoo Kim
2015-01-05 14:53 ` Christoph Lameter
2015-01-05 14:52 ` [PATCH 1/2] mm/slub: optimize alloc/free fastpath by removing preemption on/off Christoph Lameter
2015-01-06 3:03 ` Davidlohr Bueso [this message]
2015-01-06 8:09 ` Joonsoo Kim
2015-01-06 17:02 ` Davidlohr Bueso
2015-01-08 7:44 ` Joonsoo Kim
2015-01-09 3:34 ` Christoph Lameter
-- strict thread matches above, loose matches on Subject: below --
2015-01-05 8:37 Hillf Danton
2015-01-06 1:32 ` Joonsoo Kim
2015-01-06 2:25 ` Steven Rostedt
2015-01-06 8:27 ` Joonsoo Kim
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