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Thu, 13 May 2021 12:26:16 +0000 (GMT) Received: from localhost.localdomain (unknown [9.199.44.200]) by b03ledav005.gho.boulder.ibm.com (Postfix) with ESMTP; Thu, 13 May 2021 12:26:16 +0000 (GMT) Subject: Re: [RFC 1/4] drivers/nvdimm: Add perf interface to expose nvdimm performance stats To: Peter Zijlstra References: <20210512163824.255370-1-kjain@linux.ibm.com> <20210512163824.255370-2-kjain@linux.ibm.com> From: kajoljain Message-ID: <37015d53-050a-acef-2958-b1ff5d02800b@linux.ibm.com> Date: Thu, 13 May 2021 17:56:14 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: EvtomYgSIUC0jAMqMvwF4gaUntt7Qasr X-Proofpoint-GUID: EvtomYgSIUC0jAMqMvwF4gaUntt7Qasr X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.761 definitions=2021-05-13_06:2021-05-12, 2021-05-13 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 spamscore=0 impostorscore=0 phishscore=0 priorityscore=1501 clxscore=1011 suspectscore=0 malwarescore=0 bulkscore=0 mlxlogscore=999 adultscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2105130093 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: santosh@fossix.org, maddy@linux.vnet.ibm.com, ira.weiny@intel.com, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, atrajeev@linux.vnet.ibm.com, aneesh.kumar@linux.ibm.com, vaibhav@linux.ibm.com, dan.j.williams@intel.com, linuxppc-dev@lists.ozlabs.org, tglx@linutronix.de Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 5/12/21 10:57 PM, Peter Zijlstra wrote: > On Wed, May 12, 2021 at 10:08:21PM +0530, Kajol Jain wrote: >> +static void nvdimm_pmu_read(struct perf_event *event) >> +{ >> + struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu); >> + >> + /* jump to arch/platform specific callbacks if any */ >> + if (nd_pmu && nd_pmu->read) >> + nd_pmu->read(event, nd_pmu->dev); >> +} >> + >> +static void nvdimm_pmu_del(struct perf_event *event, int flags) >> +{ >> + struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu); >> + >> + /* jump to arch/platform specific callbacks if any */ >> + if (nd_pmu && nd_pmu->del) >> + nd_pmu->del(event, flags, nd_pmu->dev); >> +} >> + >> +static int nvdimm_pmu_add(struct perf_event *event, int flags) >> +{ >> + struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu); >> + >> + if (flags & PERF_EF_START) >> + /* jump to arch/platform specific callbacks if any */ >> + if (nd_pmu && nd_pmu->add) >> + return nd_pmu->add(event, flags, nd_pmu->dev); >> + return 0; >> +} > > What's the value add here? Why can't you directly set driver pointers? I > also don't really believe ->{add,del,read} can be optional and still > have a sane driver. > Hi Peter, The intend for adding these callbacks is to give flexibility to the arch/platform specific driver code to use its own routine for getting counter data or specific checks/operations. Arch/platform driver code would have different method to get the counter data like IBM pseries nmem* device which uses a hypervisor call(hcall). But yes the current read/add/del functions are not adding value. We could add an arch/platform specific function which could handle the capturing of the counter data and do the rest of the operation here, is this approach better? Thanks, Kajol Jain