From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 05/11] qspinlock: Optimize for smaller NR_CPUS Date: Mon, 07 Jul 2014 18:10:30 +0200 Message-ID: <53BAC676.5030804@redhat.com> References: <20140615124657.264658593@chello.nl> <20140615130153.483502389@chello.nl> <53A17A88.7090705@redhat.com> <20140707143503.GS6758@twins.programming.kicks-ass.net> <53BAB7E1.4010506@redhat.com> <20140707153552.GE19379@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140707153552.GE19379@twins.programming.kicks-ass.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Peter Zijlstra Cc: Waiman.Long@hp.com, linux-arch@vger.kernel.org, riel@redhat.com, gleb@redhat.com, kvm@vger.kernel.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, scott.norton@hp.com, raghavendra.kt@linux.vnet.ibm.com, paolo.bonzini@gmail.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, chegu_vinod@hp.com, david.vrabel@citrix.com, oleg@redhat.com, xen-devel@lists.xenproject.org, tglx@linutronix.de, paulmck@linux.vnet.ibm.com, torvalds@linux-foundation.org, mingo@kernel.org List-Id: virtualization@lists.linuxfoundation.org Il 07/07/2014 17:35, Peter Zijlstra ha scritto: >> > Unlike the change in patch 4, clear_pending_set_locked doesn't change how >> > qspinlock moves from a state to the next. > True, but its where we start to break up into smaller functions. And the > only reason we break them out is because we'll get different > implementations depending on NR_CPUS. > > So we can view the breakout of xchg_tail and clear_and_set_pending as > preparatory work for introducing the NR_CPUS thing. That's a different reasoning, but it's fine by me too. Paolo