From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH V2 16/19] csky: SMP support Date: Fri, 6 Jul 2018 11:39:32 +0200 Message-ID: <20180706093932.GT2476@hirez.programming.kicks-ass.net> References: <21d859826fe19aecaa2aefe3103d6d33e6f1b925.1530465326.git.ren_guo@c-sky.com> <20180705180503.GH2530@hirez.programming.kicks-ass.net> <20180706060740.GB8707@guoren> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20180706060740.GB8707@guoren> Sender: linux-kernel-owner@vger.kernel.org To: Guo Ren Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, daniel.lezcano@linaro.org, jason@lakedaemon.net, arnd@arndb.de, c-sky_gcc_upstream@c-sky.com, gnu-csky@mentor.com, thomas.petazzoni@bootlin.com, wbx@uclibc-ng.org, green.hu@gmail.com, Will Deacon List-Id: linux-arch.vger.kernel.org On Fri, Jul 06, 2018 at 02:07:40PM +0800, Guo Ren wrote: > > Please explain those mb()'s... I'm thinking you meant to use smp_mb(). > Yes, smp_mb(). Current smp_mb()&mb() is the same: sync.is. > > In next version patch, I'll seperate smp_mb() and mb() and use ld/st.barrier > instead of sync.is. Sync.is is expensive that it flush cpu's pipeline. I'll second my own call for documentation, because now there's three memory ordering instructions: "SYNC", "SYNC.IS" and "LD/ST.BARRIER" None of which have yet been explained. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:41506 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753281AbeGFJkW (ORCPT ); Fri, 6 Jul 2018 05:40:22 -0400 Date: Fri, 6 Jul 2018 11:39:32 +0200 From: Peter Zijlstra Subject: Re: [PATCH V2 16/19] csky: SMP support Message-ID: <20180706093932.GT2476@hirez.programming.kicks-ass.net> References: <21d859826fe19aecaa2aefe3103d6d33e6f1b925.1530465326.git.ren_guo@c-sky.com> <20180705180503.GH2530@hirez.programming.kicks-ass.net> <20180706060740.GB8707@guoren> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180706060740.GB8707@guoren> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Guo Ren Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, daniel.lezcano@linaro.org, jason@lakedaemon.net, arnd@arndb.de, c-sky_gcc_upstream@c-sky.com, gnu-csky@mentor.com, thomas.petazzoni@bootlin.com, wbx@uclibc-ng.org, green.hu@gmail.com, Will Deacon Message-ID: <20180706093932._SUKEVxPDU9VtMp64wPPJcWnl-62V1t38BDe7BJX1Ps@z> On Fri, Jul 06, 2018 at 02:07:40PM +0800, Guo Ren wrote: > > Please explain those mb()'s... I'm thinking you meant to use smp_mb(). > Yes, smp_mb(). Current smp_mb()&mb() is the same: sync.is. > > In next version patch, I'll seperate smp_mb() and mb() and use ld/st.barrier > instead of sync.is. Sync.is is expensive that it flush cpu's pipeline. I'll second my own call for documentation, because now there's three memory ordering instructions: "SYNC", "SYNC.IS" and "LD/ST.BARRIER" None of which have yet been explained.