From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 26 Mar 2008 07:50:23 +0100 From: Ingo Molnar Subject: Re: [PATCH 06/10] x86: reduce memory and stack usage in intel_cacheinfo Message-ID: <20080326065023.GG18301@elte.hu> References: <20080325220650.835342000@polaris-admin.engr.sgi.com> <20080325220651.683748000@polaris-admin.engr.sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080325220651.683748000@polaris-admin.engr.sgi.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Mike Travis Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andi Kleen List-ID: * Mike Travis wrote: > * Change the following static arrays sized by NR_CPUS to > per_cpu data variables: > > _cpuid4_info *cpuid4_info[NR_CPUS]; > _index_kobject *index_kobject[NR_CPUS]; > kobject * cache_kobject[NR_CPUS]; > > * Remove the local NR_CPUS array with a kmalloc'd region in > show_shared_cpu_map(). thanks Travis, i've applied this to x86.git. one observation: > static ssize_t show_shared_cpu_map(struct _cpuid4_info *this_leaf, char *buf) > { > - char mask_str[NR_CPUS]; > - cpumask_scnprintf(mask_str, NR_CPUS, this_leaf->shared_cpu_map); > - return sprintf(buf, "%s\n", mask_str); > + 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); > + } > + return n; the other changes look good, but this one looks a bit ugly and complex. We basically want to sprintf shared_cpu_map into 'buf', but we do that by first allocating a temporary buffer, print a string into it, then print that string into another buffer ... this very much smells like an API bug in cpumask_scnprintf() - why dont you create a cpumask_scnprintf_ptr() API that takes a pointer to a cpumask? Then this change would become a trivial and much more readable: - char mask_str[NR_CPUS]; - cpumask_scnprintf(mask_str, NR_CPUS, this_leaf->shared_cpu_map); - return sprintf(buf, "%s\n", mask_str); + return cpumask_scnprintf_ptr(buf, NR_CPUS, &this_leaf->shared_cpu_map); Ingo -- 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