Messages in this thread | | | Date | Mon, 15 Dec 2014 10:02:04 +0800 | From | Lai Jiangshan <> | Subject | Re: [PATCH 2/5] workqueue: update wq_numa_possible_cpumask |
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On 12/13/2014 01:18 AM, Tejun Heo wrote: > On Fri, Dec 12, 2014 at 06:19:52PM +0800, Lai Jiangshan wrote: > ... >> +static void wq_update_numa_mapping(int cpu) >> +{ >> + int node, orig_node = NUMA_NO_NODE, new_node = cpu_to_node(cpu); >> + >> + lockdep_assert_held(&wq_pool_mutex); >> + >> + if (!wq_numa_enabled) >> + return; >> + >> + /* the node of onlining CPU is not NUMA_NO_NODE */ >> + if (WARN_ON(new_node == NUMA_NO_NODE)) >> + return; >> + >> + /* test whether the NUMA node mapping is changed. */ >> + if (cpumask_test_cpu(cpu, wq_numa_possible_cpumask[new_node])) >> + return; >> + >> + /* find the origin node */ >> + for_each_node(node) { >> + if (cpumask_test_cpu(cpu, wq_numa_possible_cpumask[node])) { >> + orig_node = node; >> + break; >> + } >> + } >> + >> + /* there may be multi mappings changed, re-initial. */ >> + cpumask_clear(wq_numa_possible_cpumask[new_node]); >> + if (orig_node != NUMA_NO_NODE) >> + cpumask_clear(wq_numa_possible_cpumask[orig_node]); >> + for_each_possible_cpu(cpu) { >> + node = cpu_to_node(node); >> + if (node == new_node) >> + cpumask_set_cpu(cpu, wq_numa_possible_cpumask[new_node]); >> + else if (orig_node != NUMA_NO_NODE && node == orig_node) >> + cpumask_set_cpu(cpu, wq_numa_possible_cpumask[orig_node]); >> + } >> +} > > Let's please move this to NUMA code and properly update it on actual > mapping changes. >
Hi, TJ
I didn't get your means. What did you mean "NUMA code"? Which one did you mean?
1) "NUMA code" = system's NUMA memory hotplug code, AKA, keep the numa mapping stable
I think this is the better idea. This idea came to my mind immediately at the time I received the bug report. And after some discussions, I was told that it is too HARD to keep the numa mapping stable across multiple physical system-board/node online/offline.
This idea makes the assumption "the numa mapping is stable after system booted" as a restriction of the NUMA. And it will favor all the code outside of the numa code, otherwise (we deny the assumption like this patchset) all the code which use "cpu_to_node()" and cache the return value will have to be fixed up like this patchset.
Hi, hotplug-team, any idea to keep the numa mapping stable?
2) "NUMA code" = workqueue's NUMA code I think I already did it, the code I added was right below the code of wq_update_unbound_numa(). Or I missed something?
Thanks, Lai
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