From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21399C001E0 for ; Mon, 23 Oct 2023 13:03:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230393AbjJWNDw (ORCPT ); Mon, 23 Oct 2023 09:03:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57622 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229730AbjJWNDv (ORCPT ); Mon, 23 Oct 2023 09:03:51 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1CBBC97 for ; Mon, 23 Oct 2023 06:03:48 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D51022F4; Mon, 23 Oct 2023 06:04:28 -0700 (PDT) Received: from [10.34.100.114] (e126645.nice.arm.com [10.34.100.114]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 719F33F762; Mon, 23 Oct 2023 06:03:46 -0700 (PDT) Message-ID: Date: Mon, 23 Oct 2023 15:03:40 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 0/5] support NUMA emulation for arm64 To: Rongwei Wang , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: akpm@linux-foundation.org, willy@infradead.org, catalin.marinas@arm.com, dave.hansen@linux.intel.com, tj@kernel.org, mingo@redhat.com References: <20231012024842.99703-1-rongwei.wang@linux.alibaba.com> <57eba42c-732a-4a30-a714-5e5538f2e5d5@linux.alibaba.com> Content-Language: en-US From: Pierre Gondois In-Reply-To: <57eba42c-732a-4a30-a714-5e5538f2e5d5@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Rongwei, On 10/12/23 15:30, Rongwei Wang wrote: > > On 2023/10/12 20:37, Pierre Gondois wrote: >> Hello Rongwei, >> >> On 10/12/23 04:48, Rongwei Wang wrote: >>> A brief introduction >>> ==================== >>> >>> The NUMA emulation can fake more node base on a single >>> node system, e.g. >>> >>> one node system: >>> >>> [root@localhost ~]# numactl -H >>> available: 1 nodes (0) >>> node 0 cpus: 0 1 2 3 4 5 6 7 >>> node 0 size: 31788 MB >>> node 0 free: 31446 MB >>> node distances: >>> node   0 >>>    0:  10 >>> >>> add numa=fake=2 (fake 2 node on each origin node): >>> >>> [root@localhost ~]# numactl -H >>> available: 2 nodes (0-1) >>> node 0 cpus: 0 1 2 3 4 5 6 7 >>> node 0 size: 15806 MB >>> node 0 free: 15451 MB >>> node 1 cpus: 0 1 2 3 4 5 6 7 >>> node 1 size: 16029 MB >>> node 1 free: 15989 MB >>> node distances: >>> node   0   1 >>>    0:  10  10 >>>    1:  10  10 >>> >>> As above shown, a new node has been faked. As cpus, the realization >>> of x86 NUMA emulation is kept. Maybe each node should has 4 cores is >>> better (not sure, next to do if so). >>> >>> Why do this >>> =========== >>> >>> It seems has following reasons: >>>    (1) In x86 host, apply NUMA emulation can fake more nodes environment >>>        to test or verify some performance stuff, but arm64 only has >>>        one method that modify ACPI table to do this. It's troublesome >>>        more or less. >>>    (2) Reduce competition for some locks. Here an example we found: >>>        will-it-scale/tlb_flush1_processes -t 96 -s 10, it shows obvious >>>        hotspot on lruvec->lock when test in single environment. What's >>>        more, The performance improved greatly if test in two more nodes >>>        system. The data shows below (more is better): >>> >>> --------------------------------------------------------------------- >>>        threads/process |   1     |     12   |     24   | 48     |   96 >>> --------------------------------------------------------------------- >>>        one node        | 14 1122 | 110 5372 | 111 2615 | 79 7084  | >>> 72 4516 >>> --------------------------------------------------------------------- >>>        numa=fake=2     | 14 1168 | 144 4848 | 215 9070 | 157 0412 | >>> 142 3968 >>> --------------------------------------------------------------------- >>>                        | For concurrency 12, no lruvec->lock hotspot. >>> For 24, >>>        hotspot         | one node has 24% hotspot on lruvec->lock, but >>>                        | two nodes env hasn't. >>> --------------------------------------------------------------------- >>> >>> As for risks (e.g. numa balance...), they need to be discussed here. >>> >>> Lastly, this just is a draft, I can improve next if it's acceptable. >> >> I'm not engaging on the utility/relevance of the patch-set, but I tried >> them on an arm64 system with the 'numa=fake=2' parameter and could not > > Sorry, my fault. > > I should mention this in previous brief introduction: acpi=on numa=fake=2. > > The default patch of arm64 numa initialize is numa_init() -> > dummy_numa_init() if turn off acpi (this path has not been taken into > account yet in this patch, next will to do). > > What's more, if you test these patchset in qemu-kvm, you should add > below parameters in the script. > > object memory-backend-ram,id=mem0,size=32G \ > numa node,memdev=mem0,cpus=0-7,nodeid=0 \ > > (Above parameters just make sure SRAT table has NUMA configure, avoiding > path of numa_init() -> dummy_numa_init()) > >> see 2 nodes being created under: >>   /sys/devices/system/node/ >> Indeed it seems that even though numa_emulation() is moved to a generic >> mm/numa.c file, the function is only called from: >>   arch/x86/mm/numa.c:numa_init() >> (or maybe I'm misinterpreting the intent of the patches). > > Here drivers/base/arch_numa.c:numa_init() has called numa_emulation() (I > guess it works if you add acpi=on :-)). I don't see numa_emulation() being called from drivers/base/arch_numa.c:numa_init() I have: $ git grep numa_emulation arch/x86/mm/numa.c: numa_emulation(&numa_meminfo, numa_distance_cnt); arch/x86/mm/numa_internal.h:extern void __init numa_emulation(struct numa_meminfo *numa_meminfo, include/asm-generic/numa.h:void __init numa_emulation(struct numa_meminfo *numa_meminfo, mm/numa.c:/* Most of this file comes from x86/numa_emulation.c */ mm/numa.c: * numa_emulation - Emulate NUMA nodes mm/numa.c:void __init numa_emulation(struct numa_meminfo *numa_meminfo, int numa_dist_cnt) so from this, an arm64-based platform should not be able to call numa_emulation(). Is it possible to add a call to dump_stack() in numa_emulation() to see the call stack ? The branch I'm using is based on v6.6-rc5 and has the 5 patches applied: 2af398a87cc7 mm/numa: migrate leftover numa emulation into mm/numa.c c8e314fb23be mm/numa: support CONFIG_NUMA_EMU for arm64 335b7219d40e arch_numa: remove __init in early_cpu_to_node() d9358adf1cdc mm: percpu: fix variable type of cpu 1ffbe40a00f5 mm/numa: move numa emulation APIs into generic files 94f6f0550c62 (tag: v6.6-rc5) Linux 6.6-rc5 Regards, Pierre > > >> >> Also I had the following errors when building (still for arm64): >> mm/numa.c:862:8: error: implicit declaration of function >> 'early_cpu_to_node' is invalid in C99 >> [-Werror,-Wimplicit-function-declaration] >>         nid = early_cpu_to_node(cpu); > > It seems CONFIG_DEBUG_PER_CPU_MAPS enabled in your environment? You can > disable CONFIG_DEBUG_PER_CPU_MAPS and test it again. > > I have not test it with CONFIG_DEBUG_PER_CPU_MAPS enabled. It's very > helpful, I will fix it next time. > > If you have any questions, please let me know. > > Regards, > > -wrw > >> ^ >> mm/numa.c:862:8: note: did you mean 'early_map_cpu_to_node'? >> ./include/asm-generic/numa.h:37:13: note: 'early_map_cpu_to_node' >> declared here >> void __init early_map_cpu_to_node(unsigned int cpu, int nid); >>             ^ >> mm/numa.c:874:3: error: implicit declaration of function >> 'debug_cpumask_set_cpu' is invalid in C99 >> [-Werror,-Wimplicit-function-declaration] >>                 debug_cpumask_set_cpu(cpu, nid, enable); >>                 ^ >> mm/numa.c:874:3: note: did you mean '__cpumask_set_cpu'? >> ./include/linux/cpumask.h:474:29: note: '__cpumask_set_cpu' declared here >> static __always_inline void __cpumask_set_cpu(unsigned int cpu, struct >> cpumask *dstp) >>                             ^ >> 2 errors generated. >> >> Regards, >> Pierre >> >>> >>> Thanks! >>> >>> Rongwei Wang (5): >>>    mm/numa: move numa emulation APIs into generic files >>>    mm: percpu: fix variable type of cpu >>>    arch_numa: remove __init in early_cpu_to_node() >>>    mm/numa: support CONFIG_NUMA_EMU for arm64 >>>    mm/numa: migrate leftover numa emulation into mm/numa.c >>> >>>   arch/x86/Kconfig                          |   8 - >>>   arch/x86/include/asm/numa.h               |   3 - >>>   arch/x86/mm/Makefile                      |   1 - >>>   arch/x86/mm/numa.c                        | 216 +------------- >>>   arch/x86/mm/numa_internal.h               |  14 +- >>>   drivers/base/arch_numa.c                  |   7 +- >>>   include/asm-generic/numa.h                |  33 +++ >>>   include/linux/percpu.h                    |   2 +- >>>   mm/Kconfig                                |   8 + >>>   mm/Makefile                               |   1 + >>>   arch/x86/mm/numa_emulation.c => mm/numa.c | 333 +++++++++++++++++++++- >>>   11 files changed, 373 insertions(+), 253 deletions(-) >>>   rename arch/x86/mm/numa_emulation.c => mm/numa.c (63%) >>>