From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756604AbbJ2FoG (ORCPT ); Thu, 29 Oct 2015 01:44:06 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:35873 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751818AbbJ2FoF (ORCPT ); Thu, 29 Oct 2015 01:44:05 -0400 Subject: Re: [PATCH] recordmcount: arm64: replace the ignored mcount call into nop To: Will Deacon , Steven Rostedt References: <1446019445-14421-1-git-send-email-huawei.libin@huawei.com> <20151028041619.4e44491a@grimm.local.home> <20151028115825.GB29512@arm.com> Cc: Li Bin , catalin.marinas@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, guohanjun@huawei.com, dingtianhong@huawei.com, zhouchengming1@huawei.com From: AKASHI Takahiro Message-ID: <5631B21C.3060504@linaro.org> Date: Thu, 29 Oct 2015 14:43:56 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20151028115825.GB29512@arm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/28/2015 08:58 PM, Will Deacon wrote: > On Wed, Oct 28, 2015 at 04:16:19AM -0400, Steven Rostedt wrote: >> On Wed, 28 Oct 2015 16:04:05 +0800 >> Li Bin wrote: >> >>> By now, the recordmcount only records the function that in >>> following sections: >>> .text/.ref.text/.sched.text/.spinlock.text/.irqentry.text/ >>> .kprobes.text/.text.unlikely >>> >>> For the function that not in these sections, the call mcount >>> will be in place and not be replaced when kernel boot up. And >>> it will bring performance overhead, such as do_mem_abort (in >>> .exception.text section). This patch make the call mcount to >>> nop for this case in recordmcount. The patch itself is fine (it might be a good idea to describe what 0x94000000 means though), but I'm wondering whether we have any reason to exclude .exception.text from tracing. In my understandings, this attribute (.exception.text) is utilized solely for pretty printing in dump_backtrace(). Thanks, -Takahiro AKASHI >> I can take this in my tree with an Ack from the ARM64 maintainers. > > Looks like it does what it says on the tin: > > Acked-by: Will Deacon > > Will >