From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753944AbbESRfY (ORCPT ); Tue, 19 May 2015 13:35:24 -0400 Received: from mga03.intel.com ([134.134.136.65]:36712 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750811AbbESRfU (ORCPT ); Tue, 19 May 2015 13:35:20 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,459,1427785200"; d="scan'208";a="697279256" Date: Tue, 19 May 2015 10:33:55 -0700 (PDT) From: Vikas Shivappa X-X-Sender: vikas@vshiva-Udesk To: Borislav Petkov cc: Thomas Gleixner , Vikas Shivappa , Vikas Shivappa , x86@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, tj@kernel.org, peterz@infradead.org, Matt Fleming , "Auld, Will" , peter.zijlstra@intel.com, h.peter.anvin@intel.com, "Juvva, Kanaka D" , mtosatti@redhat.com Subject: Re: [PATCH 2/7] x86/intel_rdt: Adds support for Class of service management In-Reply-To: <20150518192057.GA23653@pd.tnic> Message-ID: References: <1431370976-31115-1-git-send-email-vikas.shivappa@linux.intel.com> <1431370976-31115-3-git-send-email-vikas.shivappa@linux.intel.com> <20150518192057.GA23653@pd.tnic> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 18 May 2015, Borislav Petkov wrote: > On Mon, May 18, 2015 at 08:41:53PM +0200, Thomas Gleixner wrote: >>>>> + } >>>>> + >>>>> + set_bit(0, rdtss_info.closmap); >>>>> + rdt_root_group.clos = 0; >>>>> + ccm = &ccmap[0]; >>>>> + bitmap_set(&ccm->cache_mask, 0, max_cbm_len); >>>>> + ccm->clos_refcnt = 1; >>>>> + >>>>> pr_info("Max bitmask length:%u,Max ClosIds: %u\n", max_cbm_len, >>>>> maxid); >>>> >>>> We surely do not want to sprinkle these all over dmesg. >>> >>> This is just printed once! how is that sprinke all over? - we have a dmsg >>> print for Cache monitoring as well when cqm is enabled. >> >> Sorry, mapped that to the wrong function. Though the message itself is >> horrible. >> >> "Max bitmask length:32,Max ClosIds: 16" >> >> With some taste and formatting applied this would read: >> >> "Max. bitmask length: 32, max. closids: 16" >> >> Can you spot the difference? > > I sure can. > > Also, I'd still like to ask about the usability of that message. What > does it bring us? > > And if the dmesg ring buffer wraps around and it gets overwritten, what > do we do then? > > So basically this message does tell us about some max bitmap length and > so on. IOW, useless, right? > > Can it be read out from CPUID maybe? If so, stuff which is interested in > it can generate it then. Yes the max bitmask and max closid can be read from cpuid. the presence of rdt and l3 cache alloc is indicated by rdt and cat_l3 in /proc/cpuinfo. So even if this message gets overwritten , user can see the feature enabled in kernel. Can be modified somthing similar to "Intel cache allocation enabled" as well. Thanks, Vikas > > -- > Regards/Gruss, > Boris. > > ECO tip #101: Trim your mails when you reply. > -- >