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Fri, 17 Jul 2020 06:00:53 +0000 (GMT) Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 370637805E; Fri, 17 Jul 2020 06:00:46 +0000 (GMT) Received: from sofia.ibm.com (unknown [9.199.61.65]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP; Fri, 17 Jul 2020 06:00:46 +0000 (GMT) Received: by sofia.ibm.com (Postfix, from userid 1000) id F13142E3225; Fri, 17 Jul 2020 11:30:11 +0530 (IST) Date: Fri, 17 Jul 2020 11:30:11 +0530 From: Gautham R Shenoy To: Srikar Dronamraju Subject: Re: [PATCH 05/11] powerpc/smp: Dont assume l2-cache to be superset of sibling Message-ID: <20200717060011.GE25851@in.ibm.com> References: <20200714043624.5648-1-srikar@linux.vnet.ibm.com> <20200714043624.5648-6-srikar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200714043624.5648-6-srikar@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-07-17_03:2020-07-16, 2020-07-17 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 mlxlogscore=999 lowpriorityscore=0 clxscore=1015 priorityscore=1501 bulkscore=0 impostorscore=0 phishscore=0 suspectscore=0 mlxscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007170038 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: ego@linux.vnet.ibm.com Cc: Nathan Lynch , Gautham R Shenoy , Oliver OHalloran , Michael Neuling , Michael Ellerman , Anton Blanchard , linuxppc-dev , Nick Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Srikar, On Tue, Jul 14, 2020 at 10:06:18AM +0530, Srikar Dronamraju wrote: > Current code assumes that cpumask of cpus sharing a l2-cache mask will > always be a superset of cpu_sibling_mask. > > Lets stop that assumption. > > Cc: linuxppc-dev > Cc: Michael Ellerman > Cc: Nick Piggin > Cc: Oliver OHalloran > Cc: Nathan Lynch > Cc: Michael Neuling > Cc: Anton Blanchard > Cc: Gautham R Shenoy > Cc: Vaidyanathan Srinivasan > Signed-off-by: Srikar Dronamraju > --- > arch/powerpc/kernel/smp.c | 28 +++++++++++++++------------- > 1 file changed, 15 insertions(+), 13 deletions(-) > > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c > index 7d430fc536cc..875f57e41355 100644 > --- a/arch/powerpc/kernel/smp.c > +++ b/arch/powerpc/kernel/smp.c > @@ -1198,6 +1198,7 @@ static bool update_mask_by_l2(int cpu, struct cpumask *(*mask_fn)(int)) > struct device_node *l2_cache, *np; > int i; > > + cpumask_set_cpu(cpu, mask_fn(cpu)); It would be good to comment why do we need to do set the CPU in the l2-mask if we don't have a l2cache domain. > l2_cache = cpu_to_l2cache(cpu); > if (!l2_cache) > return false; > @@ -1284,29 +1285,30 @@ static void add_cpu_to_masks(int cpu) > * add it to it's own thread sibling mask. > */ > cpumask_set_cpu(cpu, cpu_sibling_mask(cpu)); > + cpumask_set_cpu(cpu, cpu_core_mask(cpu)); > > for (i = first_thread; i < first_thread + threads_per_core; i++) > if (cpu_online(i)) > set_cpus_related(i, cpu, cpu_sibling_mask); > > add_cpu_to_smallcore_masks(cpu); > - /* > - * Copy the thread sibling mask into the cache sibling mask > - * and mark any CPUs that share an L2 with this CPU. > - */ > - for_each_cpu(i, cpu_sibling_mask(cpu)) > - set_cpus_related(cpu, i, cpu_l2_cache_mask); > update_mask_by_l2(cpu, cpu_l2_cache_mask); > > - /* > - * Copy the cache sibling mask into core sibling mask and mark > - * any CPUs on the same chip as this CPU. > - */ > - for_each_cpu(i, cpu_l2_cache_mask(cpu)) > - set_cpus_related(cpu, i, cpu_core_mask); > + if (pkg_id == -1) { > + struct cpumask *(*mask)(int) = cpu_sibling_mask; > + > + /* > + * Copy the sibling mask into core sibling mask and > + * mark any CPUs on the same chip as this CPU. > + */ > + if (shared_caches) > + mask = cpu_l2_cache_mask; > + Now that we decoupling the containment relationship between sibling_mask and l2-cache mask, should we set all the CPUs that are both in cpu_sibling_mask(cpu) as well as cpu_l2_mask(cpu) in cpu_core_mask ? > + for_each_cpu(i, mask(cpu)) > + set_cpus_related(cpu, i, cpu_core_mask); > > - if (pkg_id == -1) > return; > + } > > for_each_cpu(i, cpu_online_mask) > if (get_physical_package_id(i) == pkg_id) > -- > 2.17.1 > -- Thanks and Regards gautham.