From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f182.google.com (mail-pd0-f182.google.com [209.85.192.182]) by kanga.kvack.org (Postfix) with ESMTP id D96946B0035 for ; Fri, 22 Aug 2014 14:12:38 -0400 (EDT) Received: by mail-pd0-f182.google.com with SMTP id fp1so16534570pdb.13 for ; Fri, 22 Aug 2014 11:12:38 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTP id i8si41941557pdn.177.2014.08.22.11.12.37 for ; Fri, 22 Aug 2014 11:12:37 -0700 (PDT) Subject: Re: [PATCH] [v3] warn on performance-impacting configs aka. TAINT_PERFORMANCE From: Tim Chen In-Reply-To: <53F773A2.7040904@sr71.net> References: <20140821202424.7ED66A50@viggo.jf.intel.com> <1408725157.4347.14.camel@schen9-DESK> <53F773A2.7040904@sr71.net> Content-Type: text/plain; charset="UTF-8" Date: Fri, 22 Aug 2014 11:12:40 -0700 Message-ID: <1408731160.4347.26.camel@schen9-DESK> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-kernel@vger.kernel.org, dave.hansen@linux.intel.com, peterz@infradead.org, mingo@redhat.com, ak@linux.intel.com, akpm@linux-foundation.org, cl@linux.com, penberg@kernel.org, linux-mm@kvack.org, kirill@shutemov.name, lauraa@codeaurora.org On Fri, 2014-08-22 at 09:45 -0700, Dave Hansen wrote: > On 08/22/2014 09:32 AM, Tim Chen wrote: > >> > +#ifdef CONFIG_DEBUG_OBJECTS_FREE > >> > + "DEBUG_OBJECTS_FREE", > >> > +#endif > >> > +#ifdef CONFIG_DEBUG_KMEMLEAK > >> > + "DEBUG_KMEMLEAK", > >> > +#endif > >> > +#ifdef CONFIG_DEBUG_PAGEALLOC > >> > + "DEBUG_PAGEALLOC", > > I think coverage profiling also impact performance. > > So I sould also put CONFIG_GCOV_KERNEL in the list. > > Would CONFIG_GCOV_PROFILE_ALL be the better one to check? With plain > GCOV_KERNEL, I don't think we will, by default, put the coverage > information in any files and slow them down. CONFIG_GCOV_PROFILE_ALL is definitely a no no regarding to performance impact, which is mentioned in the gcov documentation. I haven't tested this, but if profiling is turned on only for a piece of code that is performance critical but not for the whole kernel, in theory performance can still be impacted with the overhead. So I think it is safer to check for CONFIG_GCOV_KERNEL, that has no reason to be turned on for any workload that's performance critical. Tim -- 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