From: kajoljain <kjain@linux.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org,
linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org,
maddy@linux.vnet.ibm.com, santosh@fossix.org,
aneesh.kumar@linux.ibm.com, vaibhav@linux.ibm.com,
dan.j.williams@intel.com, ira.weiny@intel.com,
atrajeev@linux.vnet.ibm.com, tglx@linutronix.de
Subject: Re: [RFC 1/4] drivers/nvdimm: Add perf interface to expose nvdimm performance stats
Date: Thu, 13 May 2021 17:56:14 +0530 [thread overview]
Message-ID: <37015d53-050a-acef-2958-b1ff5d02800b@linux.ibm.com> (raw)
In-Reply-To: <YJwP9ByvAcDPixVN@hirez.programming.kicks-ass.net>
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
next prev parent reply other threads:[~2021-05-13 12:26 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 16:38 [RFC 0/4] Add perf interface to expose nvdimm performance stats Kajol Jain
2021-05-12 16:38 ` [RFC 1/4] drivers/nvdimm: " Kajol Jain
2021-05-12 17:27 ` Peter Zijlstra
2021-05-13 12:26 ` kajoljain [this message]
2021-05-14 11:47 ` Peter Zijlstra
2021-05-17 6:43 ` kajoljain
2021-05-12 16:38 ` [RFC 2/4] powerpc/papr_scm: Add perf interface support Kajol Jain
2021-05-12 16:38 ` [RFC 3/4] powerpc/papr_scm: Document papr_scm sysfs event format entries Kajol Jain
2021-05-12 16:38 ` [RFC 4/4] powerpc/papr_scm: Add cpu hotplug support for nvdimm pmu device Kajol Jain
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