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Tue, 13 Feb 2024 05:28:18 +0000 (GMT) Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C463E20049; Tue, 13 Feb 2024 05:28:16 +0000 (GMT) Received: from li-c1fdab4c-355a-11b2-a85c-ef242fe9efb4.ibm.com.com (unknown [9.179.15.254]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 13 Feb 2024 05:28:16 +0000 (GMT) From: Shrikanth Hegde To: mpe@ellerman.id.au, npiggin@gmail.com Subject: [PATCH] powerpc/pseries: fix accuracy of stolen time Date: Tue, 13 Feb 2024 10:56:35 +0530 Message-Id: <20240213052635.231597-1-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.39.3 MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: uLuySvfLQsPOfW2ewn6SOjkmNFasJ7bK X-Proofpoint-ORIG-GUID: l3H3sve1MtbU7_j4zZ--sgRaWLxhsWtj X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-02-13_02,2024-02-12_03,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 spamscore=0 phishscore=0 mlxlogscore=999 impostorscore=0 suspectscore=0 clxscore=1011 mlxscore=0 lowpriorityscore=0 malwarescore=0 priorityscore=1501 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2402130039 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: srikar@linux.vnet.ibm.com, sshegde@linux.ibm.com, aneesh.kumar@kernel.org, naveen.n.rao@linux.ibm.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" powerVM hypervisor updates the VPA fields with stolen time data. It currently reports enqueue_dispatch_tb and ready_enqueue_tb for this purpose. In linux these two fields are used to report the stolen time. The VPA fields are updated at the TB frequency. On powerPC its mostly set at 512Mhz. Hence this needs a conversion to ns when reporting it back as rest of the kernel timings are in ns. This conversion is already handled in tb_to_ns function. So use that function to report accurate stolen time. Observed this issue and used an Capped Shared Processor LPAR(SPLPAR) to simplify the experiments. In all these cases, 100% VP Load is run using stress-ng workload. Values of stolen time is in percentages as reported by mpstat. With the patch values are close to expected. 6.8.rc1 +Patch 12EC/12VP 0.0 0.0 12EC/24VP 25.7 50.2 12EC/36VP 37.3 69.2 12EC/48VP 38.5 78.3 Fixes: 0e8a63132800 ("powerpc/pseries: Implement CONFIG_PARAVIRT_TIME_ACCOUNTING") Signed-off-by: Shrikanth Hegde Reviewed-by: Nicholas Piggin Reviewed-by: Srikar Dronamraju --- arch/powerpc/platforms/pseries/lpar.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) -- 2.39.3 diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 4561667832ed..bdcc428e1c2b 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -662,8 +662,12 @@ u64 pseries_paravirt_steal_clock(int cpu) { struct lppaca *lppaca = &lppaca_of(cpu); - return be64_to_cpu(READ_ONCE(lppaca->enqueue_dispatch_tb)) + - be64_to_cpu(READ_ONCE(lppaca->ready_enqueue_tb)); + /* + * VPA steal time counters are reported at TB frequency. Hence do a + * conversion to ns before returning + */ + return tb_to_ns(be64_to_cpu(READ_ONCE(lppaca->enqueue_dispatch_tb)) + + be64_to_cpu(READ_ONCE(lppaca->ready_enqueue_tb))); } #endif