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McKenney" , "Peter Zijlstra (Intel)" , Rohan McLure , Valentin Schneider , Josh Poimboeuf Subject: [PATCH v3 4/5] powerpc/smp: Avoid asym packing within thread_group of a core Date: Thu, 26 Oct 2023 15:48:39 +0530 Message-ID: <20231026101843.56784-5-srikar@linux.vnet.ibm.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231026101843.56784-1-srikar@linux.vnet.ibm.com> References: <20231026101843.56784-1-srikar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 4RAUJFwh7INvrOeh5mqVattyZ1eMcM_7 X-Proofpoint-ORIG-GUID: hrrm3O27tuqrBXtr1ZgotdXLdV7pMc66 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=2023-10-26_08,2023-10-25_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 mlxscore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 clxscore=1015 bulkscore=0 malwarescore=0 spamscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2310170001 definitions=main-2310260087 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" PowerVM Hypervisor will schedule at a core granularity. However each big core can have more than one thread_groups. For better utilization in case of a shared processor, its preferable for the scheduler to pack to the lowest core. However there is no benefit of moving a thread between two thread groups of the same core. Signed-off-by: Srikar Dronamraju --- arch/powerpc/kernel/smp.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index 27770f7f1ae5..daede8c2abc1 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -1763,6 +1763,19 @@ void __init smp_cpus_done(unsigned int max_cpus) set_sched_topology(powerpc_topology); } =20 +/* + * For asym packing, by default lower numbered CPU has higher priority. + * On shared processors, pack to lower numbered core. However avoid moving + * between thread_groups within the same core. + */ +int arch_asym_cpu_priority(int cpu) +{ + if (static_branch_unlikely(&splpar_asym_pack)) + return -cpu / threads_per_core; + + return -cpu; +} + #ifdef CONFIG_HOTPLUG_CPU int __cpu_disable(void) { --=20 2.31.1