From: Peter Zijlstra <peterz@infradead.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Mike Galbraith <bitbucket@online.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>, Andi Kleen <ak@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Arjan van de Ven <arjan@linux.intel.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [RFC][PATCH 0/5] preempt_count rework
Date: Wed, 14 Aug 2013 18:52:27 +0200 [thread overview]
Message-ID: <20130814165227.GA21191@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <520BACEA.50604@zytor.com>
On Wed, Aug 14, 2013 at 09:14:34AM -0700, H. Peter Anvin wrote:
> Even so, this_rq() uses __get_cpu_var() and takes its address, which
> turns into a sequence like:
>
> leaq __percpu_runqueues(%rip),%rax
> addq %gs:this_cpu_off,%rax
>
> ... which is better than the above but still more heavyweight than it
> would be if the pointer was itself a percpu variable.
Oh curses, this is because lea can't do segment offsets? So there's no
sane way to get addresses of per-cpu variables.
Because ideally we'd have something like:
lea %gs:__percpu_runqueues,%rax
So in this case it makes sense to also store the actual pointer; how
unfortunate.
next prev parent reply other threads:[~2013-08-14 16:52 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-14 13:15 [RFC][PATCH 0/5] preempt_count rework Peter Zijlstra
2013-08-14 13:15 ` [RFC][PATCH 1/5] sched: Introduce preempt_count accessor functions Peter Zijlstra
2013-08-14 13:15 ` [RFC][PATCH 2/5] sched: Add NEED_RESCHED to the preempt_count Peter Zijlstra
2013-08-14 13:15 ` [RFC][PATCH 3/5] sched, arch: Create asm/preempt.h Peter Zijlstra
2013-08-14 13:15 ` [RFC][PATCH 4/5] sched: Create more preempt_count accessors Peter Zijlstra
2013-08-14 13:15 ` [RFC][PATCH 5/5] sched, x86: Provide a per-cpu preempt_count implementation Peter Zijlstra
2013-08-14 13:47 ` [RFC][PATCH 0/5] preempt_count rework H. Peter Anvin
2013-08-14 15:39 ` Mike Galbraith
2013-08-14 15:43 ` H. Peter Anvin
2013-08-15 9:01 ` Mike Galbraith
2013-08-14 16:06 ` Peter Zijlstra
2013-08-14 16:14 ` H. Peter Anvin
2013-08-14 16:52 ` Peter Zijlstra [this message]
2013-08-14 16:58 ` H. Peter Anvin
2013-08-14 16:04 ` Peter Zijlstra
2013-08-14 17:31 ` Peter Zijlstra
2013-08-14 16:48 ` Andi Kleen
2013-08-14 16:55 ` Peter Zijlstra
2013-08-14 17:12 ` Andi Kleen
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