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Thu, 17 Jun 2021 11:46:07 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 00B3F11C04A; Thu, 17 Jun 2021 11:46:07 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EDD5911C052; Thu, 17 Jun 2021 11:46:05 +0000 (GMT) Received: from [9.102.31.110] (unknown [9.102.31.110]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 17 Jun 2021 11:46:05 +0000 (GMT) Subject: Re: [RFC PATCH 8/8] powerpc/papr_scm: Use FORM2 associativity details From: "Aneesh Kumar K.V" To: Daniel Henrique Barboza , David Gibson References: <20210614164003.196094-1-aneesh.kumar@linux.ibm.com> <20210614164003.196094-9-aneesh.kumar@linux.ibm.com> <87czsnoejl.fsf@linux.ibm.com> <87a6nrobf6.fsf@linux.ibm.com>

<87r1h0n3u6.fsf@linux.ibm.com> Message-ID: <1115fa70-d021-b764-6dad-fc0a04271062@linux.ibm.com> Date: Thu, 17 Jun 2021 17:16:05 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <87r1h0n3u6.fsf@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: WcNzHEfjAUiFRxKwl2wgxB9_EyGCdRYO X-Proofpoint-GUID: lHQwwL4WhUCPZQR3CAtneg5ZOjCEUqQz X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.790 definitions=2021-06-17_05:2021-06-15, 2021-06-17 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 bulkscore=0 clxscore=1015 impostorscore=0 spamscore=0 malwarescore=0 priorityscore=1501 mlxlogscore=999 suspectscore=0 adultscore=0 lowpriorityscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106170076 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: Nathan Lynch , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 6/17/21 4:41 PM, Aneesh Kumar K.V wrote: > Daniel Henrique Barboza writes: > >> On 6/17/21 4:46 AM, David Gibson wrote: >>> On Tue, Jun 15, 2021 at 12:35:17PM +0530, Aneesh Kumar K.V wrote: >>>> David Gibson writes: >>>> >>>>> On Tue, Jun 15, 2021 at 11:27:50AM +0530, Aneesh Kumar K.V wrote: >>>>>> David Gibson writes: >>>>>> >>>>>>> On Mon, Jun 14, 2021 at 10:10:03PM +0530, Aneesh Kumar K.V wrote: >>>>>>>> FORM2 introduce a concept of secondary domain which is identical to the >>>>>>>> conceept of FORM1 primary domain. Use secondary domain as the numa node >>>>>>>> when using persistent memory device. For DAX kmem use the logical domain >>>>>>>> id introduced in FORM2. This new numa node >>>>>>>> >>>>>>>> Signed-off-by: Aneesh Kumar K.V >>>>>>>> --- >>>>>>>> arch/powerpc/mm/numa.c | 28 +++++++++++++++++++++++ >>>>>>>> arch/powerpc/platforms/pseries/papr_scm.c | 26 +++++++++++++-------- >>>>>>>> arch/powerpc/platforms/pseries/pseries.h | 1 + >>>>>>>> 3 files changed, 45 insertions(+), 10 deletions(-) >>>>>>>> >>>>>>>> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c >>>>>>>> index 86cd2af014f7..b9ac6d02e944 100644 >>>>>>>> --- a/arch/powerpc/mm/numa.c >>>>>>>> +++ b/arch/powerpc/mm/numa.c >>>>>>>> @@ -265,6 +265,34 @@ static int associativity_to_nid(const __be32 *associativity) >>>>>>>> return nid; >>>>>>>> } >>>>>>>> >>>>>>>> +int get_primary_and_secondary_domain(struct device_node *node, int *primary, int *secondary) >>>>>>>> +{ >>>>>>>> + int secondary_index; >>>>>>>> + const __be32 *associativity; >>>>>>>> + >>>>>>>> + if (!numa_enabled) { >>>>>>>> + *primary = NUMA_NO_NODE; >>>>>>>> + *secondary = NUMA_NO_NODE; >>>>>>>> + return 0; >>>>>>>> + } >>>>>>>> + >>>>>>>> + associativity = of_get_associativity(node); >>>>>>>> + if (!associativity) >>>>>>>> + return -ENODEV; >>>>>>>> + >>>>>>>> + if (of_read_number(associativity, 1) >= primary_domain_index) { >>>>>>>> + *primary = of_read_number(&associativity[primary_domain_index], 1); >>>>>>>> + secondary_index = of_read_number(&distance_ref_points[1], 1); >>>>>>> >>>>>>> Secondary ID is always the second reference point, but primary depends >>>>>>> on the length of resources? That seems very weird. >>>>>> >>>>>> primary_domain_index is distance_ref_point[0]. With Form2 we would find >>>>>> both primary and secondary domain ID same for all resources other than >>>>>> persistent memory device. The usage w.r.t. persistent memory is >>>>>> explained in patch 7. >>>>> >>>>> Right, I misunderstood >>>>> >>>>>> >>>>>> With Form2 the primary domainID and secondary domainID are used to identify the NUMA nodes >>>>>> the kernel should use when using persistent memory devices. >>>>> >>>>> This seems kind of bogus. With Form1, the primary/secondary ID are a >>>>> sort of heirarchy of distance (things with same primary ID are very >>>>> close, things with same secondary are kinda-close, etc.). With Form2, >>>>> it's referring to their effective node for different purposes. >>>>> >>>>> Using the same terms for different meanings seems unnecessarily >>>>> confusing. >>>> >>>> They are essentially domainIDs. The interpretation of them are different >>>> between Form1 and Form2. Hence I kept referring to them as primary and >>>> secondary domainID. Any suggestion on what to name them with Form2? >>> >>> My point is that reusing associativity-reference-points for something >>> with completely unrelated semantics seems like a very poor choice. >> >> >> I agree that this reuse can be confusing. I could argue that there is >> precedent for that in PAPR - FORM0 puts a different spin on the same >> property as well - but there is no need to keep following existing PAPR >> practices in new spec (and some might argue it's best not to). >> >> As far as QEMU goes, renaming this property to "numa-associativity-mode" >> (just an example) is a quick change to do since we separated FORM1 and FORM2 >> code over there. >> >> Doing such a rename can also help with the issue of having to describe new >> FORM2 semantics using "least significant boundary" or "primary domain" or >> any FORM0|FORM1 related terminology. >> > > It is not just changing the name, we will then have to explain the > meaning of ibm,associativity-reference-points with FORM2 right? > > With FORM2 we want to represent the topology better > > -------------------------------------------------------------------------------- > | domainID 20 | > | --------------------------------------- | > | | NUMA node1 | | > | | | -------------------- | > | | ProcB -------> MEMC | | NUMA node40 | | > | | | | | | | > | | ---------------------------------- |--------> | PMEMD | | > | | | -------------------- | > | | | | > | --------------------------------------- | > -------------------------------------------------------------------------------- > > ibm,associativity: > { 20, 1, 40} -> PMEMD > { 20, 1, 1} -> PROCB/MEMC > > is the suggested FORM2 representation. > > We can simplify this as below too ibm,associativity: { 20, 1, 40} -> PMEMD { 20, 1 } -> PROCB/MEMC -aneesh