Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965215AbWEaWhT (ORCPT ); Wed, 31 May 2006 18:37:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965216AbWEaWhS (ORCPT ); Wed, 31 May 2006 18:37:18 -0400 Received: from smtp-out.google.com ([216.239.45.12]:33159 "EHLO smtp-out.google.com") by vger.kernel.org with ESMTP id S965215AbWEaWhR (ORCPT ); Wed, 31 May 2006 18:37:17 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=received:message-id:date:from:user-agent: x-accept-language:mime-version:to:cc:subject:references:in-reply-to: content-type:content-transfer-encoding; b=bKPEnFkkhcrvVk5GYxiSIX3SOGCDyvQFdPyO77bFZ1a+cRRyHBqMIQKhDLE/YAvQK 7CqWROVO2iAsCEwJTPWKQ== Message-ID: <447E1A7B.2000200@google.com> Date: Wed, 31 May 2006 15:36:43 -0700 From: Martin Bligh User-Agent: Mozilla Thunderbird 1.0.7 (X11/20051011) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Ingo Molnar CC: "Martin J. Bligh" , Andrew Morton , linux-kernel@vger.kernel.org, apw@shadowen.org Subject: Re: 2.6.17-rc5-mm1 References: <447DEF47.6010908@google.com> <20060531140823.580dbece.akpm@osdl.org> <20060531211530.GA2716@elte.hu> <447E0A49.4050105@mbligh.org> <20060531213340.GA3535@elte.hu> <447E0DEC.60203@mbligh.org> <20060531215315.GB4059@elte.hu> <447E11B5.7030203@mbligh.org> <20060531221242.GA5269@elte.hu> <447E16E6.7020804@google.com> <20060531223243.GC5269@elte.hu> In-Reply-To: <20060531223243.GC5269@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1507 Lines: 43 Ingo Molnar wrote: > * Martin Bligh wrote: > > >>>>OK. So what's the perf impact of the new version on a 32 cpu machine? >>>>;-) Maybe it's fine, maybe it's not. >>> >>> >>>no idea, but it shouldnt be nearly as bad as say SLAB_DEBUG. >> >>The "no idea" is hardly reassuring ;-) >>The latter point is definitely valid though, it's not an isolated issue. > > >>Adding new runs is easy. Changing the harness is hard ;-) > > > ok. How about a CONFIG_DEBUG_NO_OVERHEAD option, that would default to > disabled but which you could set to y. Then we could make all the more > expensive debug options: > > default y if !CONFIG_DEBUG_NO_OVERHEAD > > this would still mean you'd have to turn off CONFIG_DEBUG_NO_OVERHEAD, > but it would be automatically maintainable for you after that initial > effort, and we'd be careful to always flag new debugging options with > this flag, if they are expensive. And initially i'd define "expensive" > as "anything that adds runtime overhead". > > would this be acceptable to you? Sure, makes sense. I don't care which way up it is, ie CONFIG_DEBUG_OVERHEAD vs CONFIG_DEBUG_NO_OVERHEAD, as long as it's easily separable. There's probably other debug stuff we can turn on too, if we do that. M. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/