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Wed, 8 Jul 2020 08:39:53 +0000 (GMT) Received: from linux.ibm.com (unknown [9.148.202.29]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Wed, 8 Jul 2020 08:39:53 +0000 (GMT) Date: Wed, 8 Jul 2020 11:39:51 +0300 From: Mike Rapoport To: David Hildenbrand Subject: Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as EXPORT_SYMBOL_GPL Message-ID: <20200708083951.GH386073@linux.ibm.com> References: <20200707055917.143653-2-justin.he@arm.com> <20200707115454.GN5913@dhcp22.suse.cz> <20200707121302.GB9411@linux.ibm.com> <474f93e7-c709-1a13-5418-29f1777f614c@redhat.com> <20200707180043.GA386073@linux.ibm.com> <20200708052626.GB386073@linux.ibm.com> <9a009cf6-6c30-91ca-a1a5-9aa090c66631@redhat.com> <999ea296-4695-1219-6a4d-a027718f61e5@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <999ea296-4695-1219-6a4d-a027718f61e5@redhat.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-07-08_04:2020-07-08, 2020-07-08 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 cotscore=-2147483648 spamscore=0 impostorscore=0 mlxscore=0 malwarescore=0 bulkscore=0 clxscore=1015 mlxlogscore=999 priorityscore=1501 suspectscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2007080061 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200708_044008_426268_136412F0 X-CRM114-Status: GOOD ( 29.53 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kaly Xin , Jia He , Baoquan He , linux-nvdimm , Catalin Marinas , Chuhong Yuan , Linux Kernel Mailing List , Michal Hocko , Linux MM , Vishal Verma , Dave Jiang , Dan Williams , Will Deacon , Andrew Morton , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jul 08, 2020 at 10:26:41AM +0200, David Hildenbrand wrote: > On 08.07.20 09:50, Dan Williams wrote: > > On Wed, Jul 8, 2020 at 12:22 AM David Hildenbrand wrote: > >> > >>>>>>>> On Tue 07-07-20 13:59:15, Jia He wrote: > >>>>>>>>> This exports memory_add_physaddr_to_nid() for module driver to use. > >>>>>>>>> > >>>>>>>>> memory_add_physaddr_to_nid() is a fallback option to get the nid in case > >>>>>>>>> NUMA_NO_NID is detected. > >>>>>>>>> > >>>>>>>>> Suggested-by: David Hildenbrand > >>>>>>>>> Signed-off-by: Jia He > >>>>>>>>> --- > >>>>>>>>> arch/arm64/mm/numa.c | 5 +++-- > >>>>>>>>> 1 file changed, 3 insertions(+), 2 deletions(-) > >>>>>>>>> > >>>>>>>>> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c > >>>>>>>>> index aafcee3e3f7e..7eeb31740248 100644 > >>>>>>>>> --- a/arch/arm64/mm/numa.c > >>>>>>>>> +++ b/arch/arm64/mm/numa.c > >>>>>>>>> @@ -464,10 +464,11 @@ void __init arm64_numa_init(void) > >>>>>>>>> > >>>>>>>>> /* > >>>>>>>>> * We hope that we will be hotplugging memory on nodes we already know about, > >>>>>>>>> - * such that acpi_get_node() succeeds and we never fall back to this... > >>>>>>>>> + * such that acpi_get_node() succeeds. But when SRAT is not present, the node > >>>>>>>>> + * id may be probed as NUMA_NO_NODE by acpi, Here provide a fallback option. > >>>>>>>>> */ > >>>>>>>>> int memory_add_physaddr_to_nid(u64 addr) > >>>>>>>>> { > >>>>>>>>> - pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n", addr); > >>>>>>>>> return 0; > >>>>>>>>> } > >>>>>>>>> +EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid); > >>>>>>>> > >>>>>>>> Does it make sense to export a noop function? Wouldn't make more sense > >>>>>>>> to simply make it static inline somewhere in a header? I haven't checked > >>>>>>>> whether there is an easy way to do that sanely bu this just hit my eyes. > I'd be curious if what we are trying to optimize here is actually worth > optimizing. IOW, is there a well-known scenario where the dummy value on > arm64 would be problematic and is worth the effort? Well, it started with Michal's comment above that EXPORT_SYMBOL_GPL() for a stub might be an overkill. I think Jia's suggestion [1] with addition of a comment that explains why and when the stub will be used, can work for both memory_add_physaddr_to_nid() and phys_to_target_node(). But on more theoretical/fundmanetal level, I think we lack a generic abstraction similar to e.g. x86 'struct numa_meminfo' that serves as translaton of firmware supplied information into data that can be used by the generic mm without need to reimplement it for each and every arch. [1] https://lore.kernel.org/lkml/AM6PR08MB406907F9F2B13DA6DC893AD9F7670@AM6PR08MB4069.eurprd08.prod.outlook.com > I mean, in all performance relevant setups (ignoring > hv_balloon/xen-balloon/prove_store(), which also use > memory_add_physaddr_to_nid()), we should have a proper PXM/node > specified by the hardware on memory hotadd. The fallback of > memory_add_physaddr_to_nid() is not relevant in these scenarios. > > -- > Thanks, > > David / dhildenb > -- Sincerely yours, Mike. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel