From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f171.google.com (mail-pd0-f171.google.com [209.85.192.171]) by kanga.kvack.org (Postfix) with ESMTP id 4BD406B0037 for ; Tue, 21 Jan 2014 13:57:07 -0500 (EST) Received: by mail-pd0-f171.google.com with SMTP id g10so7842229pdj.2 for ; Tue, 21 Jan 2014 10:57:06 -0800 (PST) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTP id nu5si6570417pbc.148.2014.01.21.10.57.05 for ; Tue, 21 Jan 2014 10:57:05 -0800 (PST) Subject: Re: [PATCH v8 4/6] MCS Lock: Move mcs_lock/unlock function into its own From: Tim Chen In-Reply-To: <20140121104140.GA4092@gmail.com> References: <1390267471.3138.38.camel@schen9-DESK> <20140121101915.GS31570@twins.programming.kicks-ass.net> <20140121104140.GA4092@gmail.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 21 Jan 2014 10:57:03 -0800 Message-ID: <1390330623.3138.56.camel@schen9-DESK> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar Cc: Peter Zijlstra , Ingo Molnar , Andrew Morton , Thomas Gleixner , "Paul E.McKenney" , Will Deacon , linux-kernel@vger.kernel.org, linux-mm , linux-arch@vger.kernel.org, Linus Torvalds , Waiman Long , Andrea Arcangeli , Alex Shi , Andi Kleen , Michel Lespinasse , Davidlohr Bueso , Matthew R Wilcox , Dave Hansen , Rik van Riel , Peter Hurley , Raghavendra K T , George Spelvin , "H. Peter Anvin" , Arnd Bergmann , Aswin Chandramouleeswaran , Scott J Norton , "Figo.zhang" On Tue, 2014-01-21 at 11:41 +0100, Ingo Molnar wrote: > * Peter Zijlstra wrote: > > > On Mon, Jan 20, 2014 at 05:24:31PM -0800, Tim Chen wrote: > > > +EXPORT_SYMBOL_GPL(mcs_spin_lock); > > > +EXPORT_SYMBOL_GPL(mcs_spin_unlock); > > > > Do we really need the EXPORTs? The only user so far is mutex and that's > > core code. The other planned users are rwsems and rwlocks, for both it > > would be in the slow path, which is also core code. > > > > We should generally only add EXPORTs once theres a need. > > In fact I'd argue the hot path needs to be inlined. > > We only don't inline regular locking primitives because it would blow > up the kernel's size in too many critical places. > > But inlining an _internal_ locking implementation used in just a > handful of places is a no-brainer... > The original mspin_lock primitive from which mcs_spin_lock was derived has an explicit noinline annotation. The comment says that it is so that perf can properly account for time spent in the lock function. So it wasn't inlined in previous kernels when we started. For the time being, I'll just remove the EXPORT. If people feel that inline is the right way to go, then we'll leave the function in mcs_spin_lock.h and not create mcs_spin_lock.c. Tim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org