From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [patch 2/3] spinlock: allow inlined spinlocks Date: Sun, 16 Aug 2009 23:36:57 +0200 Message-ID: <20090816213657.GA2994@elte.hu> References: <20090814125801.881618121@de.ibm.com> <20090814125857.181021997@de.ibm.com> <20090816175750.GA5808@osiris.boeblingen.de.ibm.com> <20090816180631.GA23448@elte.hu> <20090816184458.GC5808@osiris.boeblingen.de.ibm.com> <20090816204831.GA23773@elte.hu> <20090816213343.GA4766@osiris.boeblingen.de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx2.mail.elte.hu ([157.181.151.9]:45770 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755960AbZHPVhE (ORCPT ); Sun, 16 Aug 2009 17:37:04 -0400 Content-Disposition: inline In-Reply-To: <20090816213343.GA4766@osiris.boeblingen.de.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Heiko Carstens Cc: Andrew Morton , Linus Torvalds , Peter Zijlstra , linux-arch@vger.kernel.org, Martin Schwidefsky , Arnd Bergmann , Horst Hartmann , Christian Ehrhardt , Nick Piggin * Heiko Carstens wrote: > On Sun, Aug 16, 2009 at 10:48:31PM +0200, Ingo Molnar wrote: > > * Heiko Carstens wrote: > > > On Sun, Aug 16, 2009 at 08:06:31PM +0200, Ingo Molnar wrote: > > > > * Heiko Carstens wrote: > > > > > > #define __spin_lock_is_small > > > > > > > > > > +unsigned long __lockfunc _spin_lock_irqsave_nested(spinlock_t *lock, int subclass) > > > > > > + __acquires(lock); > > > > > > + > > > > > > +#ifdef __spin_lock_is_small > > > > > > +#define _spin_lock(lock) __spin_lock(lock) > > > > > > +#else > > > > > > +void __lockfunc _spin_lock(spinlock_t *lock) __acquires(lock); > > > > > > +#endif > > > > > > > > Dunno - i'm somewhat wary of introducing a 2^28 variability here. > > > > (although the number of real variations is much lower - but still). > > > > > > > > What's the current situation on s390, precisely which of the 28 lock > > > > functions are a win to be inlined and which ones are a loss? Do you > > > > have a list/table perhaps? > > > > > > No list unfortunately. [...] > > > > Well, if you dont know the functions you want to inline, how > > will you make intelligent use of this facility then in s390? > > What I tried to say: in general we want to have all locking > functions inlined. This is because all our measurements show if > anything gets inlined performance improves. This is even true for > large functions. > > > Btw., i just noticed that s390 has CONFIG_PREEMPT turned on by > > default in its defconfig. Have you made your measurements with > > CONFIG_PREEMPT? If yes then the current inlining rules in > > spinlock.h will turn all the locking APIs into functions. > > All measurements were done with CONFIG_PREEMPT off. ok. ( Btw., regardless of this patch-set, i suspect you _really_ want compiler help for that - one with a global scope and which can go inline even larger functions, and even if they were declared global in the kernel. ) Ingo