From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755324AbbIHO7d (ORCPT ); Tue, 8 Sep 2015 10:59:33 -0400 Received: from mail-pa0-f49.google.com ([209.85.220.49]:33130 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755134AbbIHO7a convert rfc822-to-8bit (ORCPT ); Tue, 8 Sep 2015 10:59:30 -0400 Subject: Re: [PATCH] arm64: kernel: Use a separate stack for irq interrupts. Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: text/plain; charset=windows-1252 From: Jungseok Lee In-Reply-To: <55EE3DCB.40401@linaro.org> Date: Tue, 8 Sep 2015 23:59:50 +0900 Cc: James Morse , linux-arm-kernel@lists.infradead.org, "linux-kernel@vger.kernel.org Mailing List" Content-Transfer-Encoding: 8BIT Message-Id: References: <55EDA040.90208@arm.com> <1441636584-23174-1-git-send-email-james.morse@arm.com> <400272B6-0733-456F-95C9-9C72C597CEB5@gmail.com> <55EDB5FB.8060800@arm.com> <81D7F9F1-1552-4709-BA74-1BF15163C4A0@gmail.com> <55EE3DCB.40401@linaro.org> To: AKASHI Takahiro X-Mailer: Apple Mail (2.1283) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sep 8, 2015, at 10:45 AM, AKASHI Takahiro wrote: > Jungseok, Hi Akashi, > On 09/08/2015 01:34 AM, Jungseok Lee wrote: >> On Sep 8, 2015, at 1:06 AM, James Morse wrote: >>> On 07/09/15 16:48, Jungseok Lee wrote: >>>> On Sep 7, 2015, at 11:36 PM, James Morse wrote: >>>> >>>> Hi James, >>>> >>>>> Having to handle interrupts on top of an existing kernel stack means the >>>>> kernel stack must be large enough to accomodate both the maximum kernel >>>>> usage, and the maximum irq handler usage. Switching to a different stack >>>>> when processing irqs allows us to make the stack size smaller. >>>>> >>>>> Maximum kernel stack usage (running ltp and generating usb+ethernet >>>>> interrupts) was 7256 bytes. With this patch, the same workload gives >>>>> a maximum stack usage of 5816 bytes. >>>> >>>> I'd like to know how to measure the max stack depth. >>>> AFAIK, a stack tracer on ftrace does not work well. Did you dump a stack >>>> region and find or track down an untouched region? >>> >>> I enabled the 'Trace max stack' option under menuconfig 'Kernel Hacking' -> >>> 'Tracers', then looked in debugfs:/tracing/stack_max_size. >>> >>> What problems did you encounter? >>> (I may be missing something…) >> >> When I enabled the feature, all entries had *0* size except the last entry. >> It can be reproduced easily as looking in debugs:/tracing/stack_trace. > > I'm afraid that you have not applied one of patches in my RFC: > http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/355919.html My description is not clear. Whenever I use a stack tracer, I always put your RFC and Steve's stack tracer fix on top of my tree. Best Regards Jungseok Lee