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Thu, 19 Oct 2023 15:57:02 GMT Received: from smtpav06.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1A11C58055; Thu, 19 Oct 2023 15:57:02 +0000 (GMT) Received: from smtpav06.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8795E58043; Thu, 19 Oct 2023 15:56:58 +0000 (GMT) Received: from [9.171.84.137] (unknown [9.171.84.137]) by smtpav06.dal12v.mail.ibm.com (Postfix) with ESMTP; Thu, 19 Oct 2023 15:56:58 +0000 (GMT) Message-ID: <45a14ebb-91e7-489d-ad5d-6d39a48bc1f5@linux.vnet.ibm.com> Date: Thu, 19 Oct 2023 21:26:56 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/6] powerpc/smp: Enable Asym packing for cores on shared processor Content-Language: en-US To: Srikar Dronamraju References: <20231018163751.2423181-1-srikar@linux.vnet.ibm.com> <20231018163751.2423181-3-srikar@linux.vnet.ibm.com> From: Shrikanth Hegde In-Reply-To: <20231018163751.2423181-3-srikar@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: -gQcv_yCJE3G2YihojiZrXuZFqwuGsVL X-Proofpoint-ORIG-GUID: m52CIvECt0XNHIYaU802OfGZhxy9C-iH X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.980,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-10-19_15,2023-10-19_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 malwarescore=0 lowpriorityscore=0 mlxlogscore=999 mlxscore=0 impostorscore=0 clxscore=1011 priorityscore=1501 phishscore=0 suspectscore=0 spamscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2309180000 definitions=main-2310190134 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: , Cc: Mark Rutland , Valentin Schneider , Peter Zijlstra , linux-kernel@vger.kernel.org, Nicholas Piggin , Rohan McLure , linuxppc-dev , Josh Poimboeuf Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 10/18/23 10:07 PM, Srikar Dronamraju wrote: > If there are shared processor LPARs, underlying Hypervisor can have more > virtual cores to handle than actual physical cores. > > Starting with Power 9, a core has 2 nearly independent thread groups. > On a shared processors LPARs, it helps to pack threads to lesser number > of cores so that the overall system performance and utilization > improves. PowerVM schedules at a core level. Hence packing to fewer > cores helps. > > For example: Lets says there are two 8-core Shared LPARs that are > actually sharing a 8 Core shared physical pool, each running 8 threads > each. Then Consolidating 8 threads to 4 cores on each LPAR would help > them to perform better. This is because each of the LPAR will get > 100% time to run applications and there will no switching required by > the Hypervisor. > > To achieve this, enable SD_ASYM_PACKING flag at CACHE, MC and DIE level. This would have a conflict with tip/master. DIE has been renamed to PKG and Both changelog and code below should change DIE to PKG. > > Signed-off-by: Srikar Dronamraju > --- > Changelog: > v1->v2: Using static key instead of a variable. > > arch/powerpc/kernel/smp.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c > index 37c41297c9ce..498c2d51fc20 100644 > --- a/arch/powerpc/kernel/smp.c > +++ b/arch/powerpc/kernel/smp.c > @@ -1009,9 +1009,20 @@ static int powerpc_smt_flags(void) > */ > static int powerpc_shared_cache_flags(void) > { > + if (static_branch_unlikely(&powerpc_asym_packing)) > + return SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING; > + > return SD_SHARE_PKG_RESOURCES; > } > > +static int powerpc_shared_proc_flags(void) > +{ > + if (static_branch_unlikely(&powerpc_asym_packing)) > + return SD_ASYM_PACKING; > + > + return 0; > +} > + > /* > * We can't just pass cpu_l2_cache_mask() directly because > * returns a non-const pointer and the compiler barfs on that. > @@ -1048,8 +1059,8 @@ static struct sched_domain_topology_level powerpc_topology[] = { > { cpu_smt_mask, powerpc_smt_flags, SD_INIT_NAME(SMT) }, > #endif > { shared_cache_mask, powerpc_shared_cache_flags, SD_INIT_NAME(CACHE) }, > - { cpu_mc_mask, SD_INIT_NAME(MC) }, > - { cpu_cpu_mask, SD_INIT_NAME(DIE) }, > + { cpu_mc_mask, powerpc_shared_proc_flags, SD_INIT_NAME(MC) }, > + { cpu_cpu_mask, powerpc_shared_proc_flags, SD_INIT_NAME(DIE) }, > { NULL, }, > }; > > @@ -1687,6 +1698,8 @@ static void __init fixup_topology(void) > if (cpu_has_feature(CPU_FTR_ASYM_SMT)) { > pr_info_once("Enabling Asymmetric SMT scheduling\n"); > static_branch_enable(&powerpc_asym_packing); > + } else if (is_shared_processor() && has_big_cores) { > + static_branch_enable(&powerpc_asym_packing); > } > > #ifdef CONFIG_SCHED_SMT