From: Linus Torvalds <torvalds@linux-foundation.org>
To: Waiman Long <longman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
"the arch/x86 maintainers" <x86@kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Tim Chen <tim.c.chen@linux.intel.com>,
huang ying <huang.ying.caritas@gmail.com>
Subject: Re: [PATCH] locking/lock_events: Use this_cpu_add() when necessary
Date: Wed, 22 May 2019 12:54:13 -0700 [thread overview]
Message-ID: <CAHk-=wjit1=wf-JxUebS4_9WUCKbnfGPt0QF13-LijmumMEB-Q@mail.gmail.com> (raw)
In-Reply-To: <20190522153953.30341-1-longman@redhat.com>
On Wed, May 22, 2019 at 8:40 AM Waiman Long <longman@redhat.com> wrote:
>
> +#if defined(CONFIG_PREEMPT) && \
> + (defined(CONFIG_DEBUG_PREEMPT) || !defined(CONFIG_X86))
> +#define lockevent_percpu_inc(x) this_cpu_inc(x)
> +#define lockevent_percpu_add(x, v) this_cpu_add(x, v)
Why that CONFIG_X86 special case?
On x86, the regular non-underscore versionm is perfectly fine, and the
underscore is no faster or simpler.
So just make it be
#if defined(CONFIG_PREEMPT)
.. non-underscore versions..
#else
.. underscore versions ..
#endif
and realize that x86 simply doesn't _care_. On x86, it will be one
single instruction regardless.
Non-x86 may prefer the underscore versions for the non-preempt case.
Linus
next prev parent reply other threads:[~2019-05-22 19:54 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-22 15:39 [PATCH] locking/lock_events: Use this_cpu_add() when necessary Waiman Long
2019-05-22 19:54 ` Linus Torvalds [this message]
2019-05-22 20:50 ` Waiman Long
2019-05-23 14:58 ` Will Deacon
2019-05-24 17:00 ` Waiman Long
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