From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751172AbeEVEba (ORCPT ); Tue, 22 May 2018 00:31:30 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:44584 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750709AbeEVEb2 (ORCPT ); Tue, 22 May 2018 00:31:28 -0400 Date: Tue, 22 May 2018 10:01:19 +0530 From: Gautham R Shenoy To: Michael Ellerman Cc: Gautham R Shenoy , Michael Neuling , Benjamin Herrenschmidt , Vaidyanathan Srinivasan , Akshay Adiga , Shilpasri G Bhat , Balbir Singh , "Oliver O'Halloran" , Nicholas Piggin , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] powerpc: Detect the presence of big-core with interleaved threads Reply-To: ego@linux.vnet.ibm.com References: <1526037444-22876-1-git-send-email-ego@linux.vnet.ibm.com> <1526037444-22876-2-git-send-email-ego@linux.vnet.ibm.com> <1526268071.30369.20.camel@neuling.org> <20180516043516.GA14826@in.ibm.com> <87k1s1xg0z.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87k1s1xg0z.fsf@concordia.ellerman.id.au> User-Agent: Mutt/1.5.23 (2014-03-12) X-TM-AS-GCONF: 00 x-cbid: 18052204-0004-0000-0000-00001421454F X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009064; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000261; SDB=6.01035843; UDB=6.00529854; IPR=6.00814971; MB=3.00021230; MTD=3.00000008; XFM=3.00000015; UTC=2018-05-22 04:31:26 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18052204-0005-0000-0000-0000874CAC9D Message-Id: <20180522043119.GA5213@in.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-05-22_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1805220052 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Michael, On Fri, May 18, 2018 at 11:14:04PM +1000, Michael Ellerman wrote: > Gautham R Shenoy writes: > ... > >> > @@ -565,7 +615,16 @@ void __init smp_setup_cpu_maps(void) > >> > vdso_data->processorCount = num_present_cpus(); > >> > #endif /* CONFIG_PPC64 */ > >> > > >> > - /* Initialize CPU <=> thread mapping/ > >> > + dn = of_find_node_by_type(NULL, "cpu"); > >> > + if (dn) { > >> > + if (check_for_interleaved_big_core(dn)) { > >> > + has_interleaved_big_core = true; > >> > + pr_info("Detected interleaved big-cores\n"); > >> > >> Is there a runtime way to check this also? If the dmesg buffer overflows, we > >> lose this. > > > > Where do you suggest we put this ? Should it be a part of > > /proc/cpuinfo ? > > Hmm, it'd be nice not to pollute it with more junk. > > Can you just look at the pir files in sysfs? Sure Michael. I will explore this option. If we add a file called l1cache_thread_group, then the siblings of the big-core that share the L1-cache can be described as follows. # cd /sys/devices/system/cpu # grep . cpu[0-7]/l1cache_thread_group cpu0/l1cache_thread_group:0,2,4,6 cpu1/l1cache_thread_group:1,3,5,7 cpu2/l1cache_thread_group:0,2,4,6 cpu3/l1cache_thread_group:1,3,5,7 cpu4/l1cache_thread_group:0,2,4,6 cpu5/l1cache_thread_group:1,3,5,7 cpu6/l1cache_thread_group:0,2,4,6 cpu7/l1cache_thread_group:1,3,5,7 > > eg. on a normal system: > > # cd /sys/devices/system/cpu > # grep . cpu[0-7]/pir > cpu0/pir:20 > cpu1/pir:21 > cpu2/pir:22 > cpu3/pir:23 > cpu4/pir:24 > cpu5/pir:25 > cpu6/pir:26 > cpu7/pir:27 > > > cheers >