Messages in this thread | | | Date | Thu, 12 Oct 2023 14:37:43 +0200 | Subject | Re: [PATCH RFC 0/5] support NUMA emulation for arm64 | From | Pierre Gondois <> |
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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 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).
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); ^ 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%) >
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