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Thu, 17 Jun 2021 11:11:17 +0000 (GMT) Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C7FD12805C; Thu, 17 Jun 2021 11:11:15 +0000 (GMT) Received: from skywalker.linux.ibm.com (unknown [9.102.31.110]) by b01ledav001.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 17 Jun 2021 11:11:15 +0000 (GMT) X-Mailer: emacs 28.0.50 (via feedmail 11-beta-1 I) From: "Aneesh Kumar K.V" To: Daniel Henrique Barboza , David Gibson Subject: Re: [RFC PATCH 8/8] powerpc/papr_scm: Use FORM2 associativity details In-Reply-To: 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>

Date: Thu, 17 Jun 2021 16:41:13 +0530 Message-ID: <87r1h0n3u6.fsf@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: dz3rie_v4iXd4dAQP4Sh_Yzde1jwlqDL X-Proofpoint-GUID: kVa5ES6gg5PLSqfGvPLz71Ym9fowwOrB 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-2106170074 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" 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. -aneesh