Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757609AbYC1STr (ORCPT ); Fri, 28 Mar 2008 14:19:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755672AbYC1STk (ORCPT ); Fri, 28 Mar 2008 14:19:40 -0400 Received: from relay1.sgi.com ([192.48.171.29]:46255 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755060AbYC1STj (ORCPT ); Fri, 28 Mar 2008 14:19:39 -0400 Message-ID: <47ED36B9.6000508@sgi.com> Date: Fri, 28 Mar 2008 11:19:37 -0700 From: Mike Travis User-Agent: Thunderbird 2.0.0.6 (X11/20070801) MIME-Version: 1.0 To: Bert Wesarg CC: Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] x86: modify show_shared_cpu_map in intel_cacheinfo References: <20080327231654.284673000@polaris-admin.engr.sgi.com> <20080327231654.599276000@polaris-admin.engr.sgi.com> <36ca99e90803280201i708ce9b7y293a2c68e733f088@mail.gmail.com> <47ED0343.1070708@sgi.com> <36ca99e90803280754p1fbedbccp366366f0240fe5cc@mail.gmail.com> In-Reply-To: <36ca99e90803280754p1fbedbccp366366f0240fe5cc@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3597 Lines: 85 Bert Wesarg wrote: > On Fri, Mar 28, 2008 at 3:40 PM, Mike Travis wrote: >> Bert Wesarg wrote: >> > On Fri, Mar 28, 2008 at 12:16 AM, Mike Travis wrote: >> >> Used cpulist_scnprintf to print cpus on a leaf instead of requiring >> >> a new "cpumask_scnprintf_len" function to determine the size of >> >> the temporary buffer. cpulist_scnprintf can be used to print directly >> >> to the output buffer, eliminating the need for the temporary buffer. >> >> >> >> Based on: >> >> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git >> >> git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-x86.git >> >> >> >> Signed-off-by: Mike Travis >> >> --- >> >> arch/x86/kernel/cpu/intel_cacheinfo.c | 25 +++++++++++++++++-------- >> >> 1 file changed, 17 insertions(+), 8 deletions(-) >> >> >> >> --- linux.trees.git.orig/arch/x86/kernel/cpu/intel_cacheinfo.c >> >> +++ linux.trees.git/arch/x86/kernel/cpu/intel_cacheinfo.c >> >> @@ -593,14 +593,23 @@ static ssize_t show_size(struct _cpuid4_ >> >> >> >> static ssize_t show_shared_cpu_map(struct _cpuid4_info *this_leaf, char *buf) >> >> { >> >> - int n = 0; >> >> - int len = cpumask_scnprintf_len(nr_cpu_ids); >> >> - char *mask_str = kmalloc(len, GFP_KERNEL); >> >> - >> >> - if (mask_str) { >> >> - cpumask_scnprintf(mask_str, len, this_leaf->shared_cpu_map); >> >> - n = sprintf(buf, "%s\n", mask_str); >> >> - kfree(mask_str); >> >> + /* >> >> + * cpulist_scnprintf() has the advantage of compressing >> >> + * consecutive cpu numbers into a single range which seems >> >> + * appropriate for cpus on a leaf. This will change what is >> >> + * output so scripts that process the output will have to change. >> > So this breaks user space? >> > >> > Bert >> >> Potentially, yes. But I suspect with 4096 cpus, user scripts will have >> to change anyways. Currently it is represented as sets of 32 bit mask >> outputs with comma separators, so 1152 characters would be output. > But you can declare it as a programming error on user space side. If > you change the format, the brown-paper-bag is yours. > >> Is there a special notice I should provide to announce this change? > I hope so. At least lwn.net has an API changes site: > > http://lwn.net/Articles/2.6-kernel-api/ I did look at that site. Besides being "kind of" out of date (last mod: 10/19/07), it didn't appear to track changes in information displayed by proc/sysfs functions. > > I also looked into MAINTAINERS, but it seems there is no official API > 'maintainer'. > >> (And this output does conform with other syntax for printing and parsing >> strings of bits.) > Aren't the most cpumaps (like cpu/cpu*/topology/*_siblings or > node/node*/cpumap) bitmasks? I did an informal survey and you are right, the majority of references do use cpumask_scnprintf instead of cpulist_scnprintf. Maybe the later function was added later? To me though, it would seem that: 240-255 is more readable than: 00000000,00000000,00000000,00000000,00000000,00000000,00000000,0000ffff And as I mentioned, bitmask_parselist() [libbitmask(3)] does parse the output. Thanks, Mike -- 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/