Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760071AbcCDUEn (ORCPT ); Fri, 4 Mar 2016 15:04:43 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:38102 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759003AbcCDUEl (ORCPT ); Fri, 4 Mar 2016 15:04:41 -0500 Date: Fri, 4 Mar 2016 12:04:39 -0800 From: Andrew Morton To: Joonsoo Kim Cc: Vlastimil Babka , Michal Nazarewicz , Minchan Kim , Mel Gorman , "Kirill A. Shutemov" , Sergey Senozhatsky , Steven Rostedt , Linux Memory Management List , LKML , linux-api@vger.kernel.org, Joonsoo Kim Subject: Re: [PATCH v4 2/2] mm/page_ref: add tracepoint to track down page reference manipulation Message-Id: <20160304120439.a38a15e0fe5b989fe5b8edfc@linux-foundation.org> In-Reply-To: References: <1456448282-897-1-git-send-email-iamjoonsoo.kim@lge.com> <1456448282-897-2-git-send-email-iamjoonsoo.kim@lge.com> <56D71BB2.5060503@suse.cz> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2369 Lines: 58 On Thu, 3 Mar 2016 16:43:49 +0900 Joonsoo Kim wrote: > > Acked-by: Vlastimil Babka > > > >> +config DEBUG_PAGE_REF > >> + bool "Enable tracepoint to track down page reference manipulation" > >> + depends on DEBUG_KERNEL > >> + depends on TRACEPOINTS > >> + ---help--- > >> + This is the feature to add tracepoint for tracking down page > >> reference > >> + manipulation. This tracking is useful to diagnosis functional > >> failure > >> + due to migration failure caused by page reference mismatch. Be > > > > > > OK. > > > >> + careful to turn on this feature because it could bloat some > >> kernel > >> + text. In my configuration, it bloats 30 KB. Although kernel text > >> will > >> + be bloated, there would be no runtime performance overhead if > >> + tracepoint isn't enabled thanks to jump label. > > > > > > I would just write something like: > > > > Enabling this feature adds about 30 KB to the kernel code, but runtime > > performance overhead is virtually none until the tracepoints are actually > > enabled. > > Okay, better! > Andrew, do you want fixup patch from me or could you simply handle it? > This? --- a/mm/Kconfig.debug~mm-page_ref-add-tracepoint-to-track-down-page-reference-manipulation-fix-3-fix +++ a/mm/Kconfig.debug @@ -82,10 +82,9 @@ config DEBUG_PAGE_REF depends on DEBUG_KERNEL depends on TRACEPOINTS ---help--- - This is the feature to add tracepoint for tracking down page reference - manipulation. This tracking is useful to diagnosis functional failure - due to migration failure caused by page reference mismatch. Be - careful to turn on this feature because it could bloat some kernel - text. In my configuration, it bloats 30 KB. Although kernel text will - be bloated, there would be no runtime performance overhead if - tracepoint isn't enabled thanks to jump label. + This is a feature to add tracepoint for tracking down page reference + manipulation. This tracking is useful to diagnose functional failure + due to migration failures caused by page reference mismatches. Be + careful when enabling this feature because it adds about 30 KB to the + kernel code. However the runtime performance overhead is virtually + nil until the tracepoints are actually enabled. _