From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755398AbcIMNVA (ORCPT ); Tue, 13 Sep 2016 09:21:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45502 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750747AbcIMNU6 (ORCPT ); Tue, 13 Sep 2016 09:20:58 -0400 Date: Tue, 13 Sep 2016 08:20:55 -0500 From: Josh Poimboeuf To: Byungchul Park Cc: peterz@infradead.org, mingo@kernel.org, tglx@linutronix.de, walken@google.com, boqun.feng@gmail.com, kirill@shutemov.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, npiggin@gmail.com Subject: Re: [PATCH v3 02/15] x86/dumpstack: Add save_stack_trace()_fast() Message-ID: <20160913132055.3og4jxc4npqa6cfa@treble> References: <1473759914-17003-1-git-send-email-byungchul.park@lge.com> <1473759914-17003-3-git-send-email-byungchul.park@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1473759914-17003-3-git-send-email-byungchul.park@lge.com> User-Agent: Mutt/1.6.0.1 (2016-04-01) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Tue, 13 Sep 2016 13:20:57 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 13, 2016 at 06:45:01PM +0900, Byungchul Park wrote: > In non-oops case, it's usually not necessary to check all words of stack > area to extract backtrace. Instead, we can achieve it by tracking frame > pointer. So made it possible to save stack trace lightly in normal case. > > I measured its ovehead and printed its difference of sched_clock() with > my QEMU x86 machine. The latency was improved over 80% when > trace->max_entries = 5. Again this code will (probably) be obsolete soon. And another quote from my previous review: So how about we change save_stack_trace() to use print_context_stack() for CONFIG_FRAME_POINTER=n and print_context_stack_bp() for CONFIG_FRAME_POINTER=y? That would preserve the existing behavior, no? -- Josh