linux-kernel - Re: [PATCH v6 0/4] Add perf interface to expose nvdimm

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Message-ID: <a41bb801-7062-c625-3ec2-75345b927851@linux.ibm.com>
Date:   Fri, 25 Feb 2022 14:09:41 +0530
From:   kajoljain <kjain@...ux.ibm.com>
To:     Aneesh Kumar K V <aneesh.kumar@...ux.ibm.com>,
        Nageswara Sastry <rnsastry@...ux.ibm.com>, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org, nvdimm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        dan.j.williams@...el.com, ira.weiny@...el.com,
        vishal.l.verma@...el.com
Cc:     vaibhav@...ux.ibm.com, santosh@...six.org, maddy@...ux.ibm.com,
        tglx@...utronix.de, atrajeev@...ux.vnet.ibm.com
Subject: Re: [PATCH v6 0/4] Add perf interface to expose nvdimm



On 2/25/22 13:17, Aneesh Kumar K V wrote:
> On Fri, 2022-02-25 at 12:08 +0530, kajoljain wrote:
>>
>>
>> On 2/25/22 11:25, Nageswara Sastry wrote:
>>>
>>>
>>> On 17/02/22 10:03 pm, Kajol Jain wrote:
>>>>
> ....
>>>>
>>>> Changelog
>>>
>>> Tested these patches with the automated tests at
>>> avocado-misc-tests/perf/perf_nmem.py
>>> URL:
>>> https://github.com/avocado-framework-tests/avocado-misc-tests/blob/master/perf/perf_nmem.py
>>>
>>>
>>> 1. On the system where target id and online id were different then
>>> not
>>> seeing value in 'cpumask' and those tests failed.
>>>
>>> Example:
>>> Log from dmesg
>>> ...
>>> papr_scm ibm,persistent-memory:ibm,pmemory@...00003: Region
>>> registered
>>> with target node 1 and online node 0
>>> ...
>>
>> Hi Nageswara Sastry,
>>        Thanks for testing the patch set. Yes you right, incase target
>> node id and online node id is different, it can happen when target
>> node is not online and hence can cause this issue, thanks for
>> pointing
>> it.
>>
>> Function dev_to_node will return node id for a given nvdimm device
>> which
>> can be offline in some scenarios. We should use numa node id return
>> by
>> numa_map_to_online_node function in that scenario. This function
>> incase
>> given node is offline, it will lookup for next closest online node
>> and
>> return that nodeid.
>>
>> Can you try with below change and see, if you are still getting this
>> issue. Please let me know.
>>
>> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c
>> b/arch/powerpc/platforms/pseries/papr_scm.c
>> index bdf2620db461..4dd513d7c029 100644
>> --- a/arch/powerpc/platforms/pseries/papr_scm.c
>> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
>> @@ -536,7 +536,7 @@ static void papr_scm_pmu_register(struct
>> papr_scm_priv *p)
>>                                 PERF_PMU_CAP_NO_EXCLUDE;
>>
>>         /*updating the cpumask variable */
>> -       nodeid = dev_to_node(&p->pdev->dev);
>> +       nodeid = numa_map_to_online_node(dev_to_node(&p->pdev->dev));
>>         nd_pmu->arch_cpumask = *cpumask_of_node(nodeid);
>>
>>>
> 
> Can you use p->region->numa_node? 

Hi Aneesh,
      Thanks for reviewing the changes. Actually we can't use numa_node
field of region structure directly inside papr_scm.c as we will get
dereferencing issue

Result of build with this change:

arch/powerpc/platforms/pseries/papr_scm.c: In function
'papr_scm_pmu_register':
arch/powerpc/platforms/pseries/papr_scm.c:539:21: error: dereferencing
pointer to incomplete type 'struct nd_region'
  nodeid = &p->region->numa_node;
                     ^~
make[3]: *** [scripts/Makefile.build:288:
arch/powerpc/platforms/pseries/papr_scm.o] Error 1
make[2]: *** [scripts/Makefile.build:550:
arch/powerpc/platforms/pseries] Erro

This is because, this structure is defined inside drivers/nvdimm/nd.h
code which is not included in this file.

So, thats why I am using
`numa_map_to_online_node(dev_to_node(&p->pdev->dev));` directly.

Let me know if you are ok with initial change.

Thanks,
Kajol Jain

> 
> -aneesh
> 
>