From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Date: Fri, 19 Mar 2010 01:57:57 +0000 Subject: Re: [BUG] percpu misaligned allocation Message-Id: <20100318.185757.39197211.davem@davemloft.net> List-Id: References: <4BA1F2BA.30604@kernel.org> <20100318.175413.183069013.davem@davemloft.net> <20100319013119.GB22095@nowhere> In-Reply-To: <20100319013119.GB22095@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: fweisbec@gmail.com Cc: tj@kernel.org, sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org From: Frederic Weisbecker Date: Fri, 19 Mar 2010 02:31:22 +0100 > On Thu, Mar 18, 2010 at 05:54:13PM -0700, David Miller wrote: >> From: Tejun Heo >> Date: Thu, 18 Mar 2010 18:30:34 +0900 >> >> > >> > if (!total_profile_count) { >> > - buf = (char *)alloc_percpu(perf_trace_t); >> > + buf = (char *)__alloc_percpu(sizeof(perf_trace_t), >> > + __alignof__(unsigned long)); >> > if (!buf) >> > goto fail_buf; >> >> Why not make perf_trace_t have the proper alignment? > > > So, making perf_trace_t as align(8) would do the trick? > I lack the knowledge about alignment layout for archs that > need aligned accesses. > At a first glance, what I would except is that every buffer > has a base address aligned, no? Make it of the largest type that could appeat in a trace entry. I would use u64 so something like: u64 [FTRACE_MAX_PROFILE_SIZE / sizeof(u64)] From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753123Ab0CSB5h (ORCPT ); Thu, 18 Mar 2010 21:57:37 -0400 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:39738 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752818Ab0CSB5f (ORCPT ); Thu, 18 Mar 2010 21:57:35 -0400 Date: Thu, 18 Mar 2010 18:57:57 -0700 (PDT) Message-Id: <20100318.185757.39197211.davem@davemloft.net> To: fweisbec@gmail.com Cc: tj@kernel.org, sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [BUG] percpu misaligned allocation From: David Miller In-Reply-To: <20100319013119.GB22095@nowhere> References: <4BA1F2BA.30604@kernel.org> <20100318.175413.183069013.davem@davemloft.net> <20100319013119.GB22095@nowhere> X-Mailer: Mew version 6.3 on Emacs 23.1 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Frederic Weisbecker Date: Fri, 19 Mar 2010 02:31:22 +0100 > On Thu, Mar 18, 2010 at 05:54:13PM -0700, David Miller wrote: >> From: Tejun Heo >> Date: Thu, 18 Mar 2010 18:30:34 +0900 >> >> > >> > if (!total_profile_count) { >> > - buf = (char *)alloc_percpu(perf_trace_t); >> > + buf = (char *)__alloc_percpu(sizeof(perf_trace_t), >> > + __alignof__(unsigned long)); >> > if (!buf) >> > goto fail_buf; >> >> Why not make perf_trace_t have the proper alignment? > > > So, making perf_trace_t as align(8) would do the trick? > I lack the knowledge about alignment layout for archs that > need aligned accesses. > At a first glance, what I would except is that every buffer > has a base address aligned, no? Make it of the largest type that could appeat in a trace entry. I would use u64 so something like: u64 [FTRACE_MAX_PROFILE_SIZE / sizeof(u64)]