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Mon, 12 Oct 2026 10:20:51 +0000 (GMT) Received: from li-7bb28a4c-2dab-11b2-a85c-887b5c60d769.ibm.com.com (unknown [9.124.215.77]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 12 Oct 2026 10:20:51 +0000 (GMT) From: Shrikanth Hegde To: maddy@linux.ibm.com, linuxppc-dev@lists.ozlabs.org, peterz@infradead.org, tim.c.chen@linux.intel.com Cc: sshegde@linux.ibm.com, christophe.leroy@csgroup.eu, linux-kernel@vger.kernel.org, ritesh.list@gmail.com, kprateek.nayak@amd.com, yu.c.chen@intel.com, vineethr@linux.ibm.com, vincent.guittot@linaro.org, srikar@linux.ibm.com, npiggin@gmail.com, mpe@ellerman.id.au Subject: [PATCH 2/4] powerpc/topology: Add docs for llc_override Date: Mon, 12 Oct 2026 15:50:35 +0530 Message-ID: <20261012102037.2477378-3-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20261012102037.2477378-1-sshegde@linux.ibm.com> References: <20261012102037.2477378-1-sshegde@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: D00o8eQo1I5r_OUBgNR4TM6igOoIh_zm X-Proofpoint-ORIG-GUID: cue31ZNCDUOhHaSWz9uV0JPq7rXszquz X-Authority-Analysis: v=2.4 cv=aqInmiZV c=1 sm=1 tr=0 ts=6accb48d cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=goSn6fUrnbwpz7W_l2oA:9 X-Proofpoint-Spam-Info: AW1haW4tMjYxMDEyMDA0MCBTYWx0ZWRfX9aWDIc4qItRz RpkRNHG86foXdlPfCig8dgD/nchbdOTCiK90hxrnwZIH7LTdCgPgJEkl4MfgzIiKzeHSw5+bvEM Knj52vhenh549ZA0vrRtrhEoN2K8Nlk= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDEyMDA0MCBTYWx0ZWRfX59MHEgoRBjbx iYlLp5V+uM219zBggafAzsj7YVA+tLuNQtWmIxkEgDpeE7k6jlBVf7AibbsXZIH4tqdlLB3QKi4 0oUKqo71ImeYzpreCMK1GnThC259dr/gNWani5my6jMrCVgTG5XIn4gzjSFaNk8D++0ENpPxLPJ XcMJ+wHy+udeO5Fp8Ph2a/5udwQBuXiwlzzeRQvmboAqTSqKuvlL256nbyChbPAa0XkFUSKEeyM XQd0i/2+Rl0tLDhS78gxcjq/ZrdaLU6uux8FjGxpNfTb/WhPTUmHTeXccT5mTPbIFRbmUXG6C6d jtmivh+m+v+FMz7yzNa7tvUaeOsmIhUGR5zLFBXAl4U7oipr8auQ0BUxjGo+LkiSLdI8AoAaDgp NwQ3lcRBDDB9FJrE6gTTSTRBcAlDj+NfxI+E1IVeF2R9T9m/03HmJ7tfp06xHyXZkyWB/rABERb jAedTmoHBdHuGyySTMQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-10-12_03,2026-10-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 clxscore=1015 spamscore=0 malwarescore=0 suspectscore=0 bulkscore=0 adultscore=0 impostorscore=0 priorityscore=1501 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610120040 Provide documentation for the newly introduced debug knob named as llc_override. This may help one if they want to experiment with cache aware scheduling. Signed-off-by: Shrikanth Hegde --- Documentation/arch/powerpc/index.rst | 1 + Documentation/arch/powerpc/topology.rst | 27 +++++++++++++++++++++++++ 2 files changed, 28 insertions(+) create mode 100644 Documentation/arch/powerpc/topology.rst diff --git a/Documentation/arch/powerpc/index.rst b/Documentation/arch/powerpc/index.rst index 40419bea8e10..0f4caf50a9e7 100644 --- a/Documentation/arch/powerpc/index.rst +++ b/Documentation/arch/powerpc/index.rst @@ -33,6 +33,7 @@ powerpc qe_firmware syscall64-abi transactional_memory + topology ultravisor vas-api vcpudispatch_stats diff --git a/Documentation/arch/powerpc/topology.rst b/Documentation/arch/powerpc/topology.rst new file mode 100644 index 000000000000..9ed3cf7ade69 --- /dev/null +++ b/Documentation/arch/powerpc/topology.rst @@ -0,0 +1,27 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. _topology: + + +llc_override +============== + +Override the scheduler-visible LLC domain on PowerPC. + +Having LLC(last level cache) at MC/PKG helps to experiment with new +scheduler feature called cache aware scheduling which expects LLC to have +at least more than 1 core. Scheduler uses notion of LLC for wakeup and +load balancing decisions. + +Accepted values are: + + 0 Disable the override and use the platform default. + smt LLC will be at SMT domain. + mc LLC will be at MC domain, including at SMT domains. + pkg LLC will be at PKG domain, including at MC and SMT domains, + +Writing a new value rebuilds the scheduler domains. One can check the +domain flags and look for SD_SHARE_LLC to confirm if it took effect. + +Note that this doesn't change HW cache topology. It is only a debug knob +to experiment with scheduler related functionalities. So set it to sensible +values. Also note that there is no performance guarantees across the values. -- 2.52.0