From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yb0-f200.google.com (mail-yb0-f200.google.com [209.85.213.200]) by kanga.kvack.org (Postfix) with ESMTP id 1753F6B025E for ; Tue, 13 Sep 2016 09:20:59 -0400 (EDT) Received: by mail-yb0-f200.google.com with SMTP id c79so44882889ybf.2 for ; Tue, 13 Sep 2016 06:20:59 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id l129si5898015ybc.276.2016.09.13.06.20.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 13 Sep 2016 06:20:58 -0700 (PDT) Date: Tue, 13 Sep 2016 08:20:55 -0500 From: Josh Poimboeuf 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org