From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753100AbbIGQGl (ORCPT ); Mon, 7 Sep 2015 12:06:41 -0400 Received: from foss.arm.com ([217.140.101.70]:51679 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750818AbbIGQGj (ORCPT ); Mon, 7 Sep 2015 12:06:39 -0400 Message-ID: <55EDB5FB.8060800@arm.com> Date: Mon, 07 Sep 2015 17:06:19 +0100 From: James Morse User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.6.0 MIME-Version: 1.0 To: Jungseok Lee CC: "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] arm64: kernel: Use a separate stack for irq interrupts. References: <55EDA040.90208@arm.com> <1441636584-23174-1-git-send-email-james.morse@arm.com> <400272B6-0733-456F-95C9-9C72C597CEB5@gmail.com> In-Reply-To: <400272B6-0733-456F-95C9-9C72C597CEB5@gmail.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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...) Thanks, James