[PATCH] NUMA: Early use of cpu_to_node() returns 0 instead of the correct node id
Shijie Huang
shijie at amperemail.onmicrosoft.com
Thu Jan 18 23:02:29 PST 2024
在 2024/1/19 14:46, Shijie Huang 写道:
>
> 在 2024/1/19 12:42, Yury Norov 写道:
>> This adds another level of indirection, I think. Currently cpu_to_node
>> is a simple inliner. After the patch it would be a real function with
>> all the associate overhead. Can you share a bloat-o-meter output here?
> #./scripts/bloat-o-meter vmlinux vmlinux.new
> add/remove: 6/1 grow/shrink: 61/51 up/down: 1168/-588 (580)
> Function old new delta
> numa_update_cpu 148 244 +96
>
> ...................................................................................................................................(to
> many to skip)
>
> Total: Before=32990130, After=32990710, chg +0.00%
>
>
>>
>> Regardless, I don't think that the approach is correct. As per your
>> description, some initialization functions erroneously call
>> cpu_to_node() instead of early_cpu_to_node() which exists specifically
>> for that case.
sorry, I missed something.
I am not sure if the early_cpu_to_node() works on all ARCHs.
Thanks
Huang Shijie
>>
>> If the above correct, it's clearly a caller problem, and the fix is to
>> simply switch all those callers to use early version.
>
> It is easy to change to early_cpu_to_node() for sched_init(),
> init_sched_fair_class()
>
> and workqueue_init_early(). These three places call the cpu_to_node()
> in the __init function.
>
>
> But it is a little hard to change the early_trace_init(), since it
> calls cpu_to_node in the deep
>
> function stack:
>
> early_trace_init() --> ring_buffer_alloc() -->rb_allocate_cpu_buffer()
>
>
> For early_trace_init(), we need to change more code.
>
>
> Anyway, If we think it is not a good idea to change the common code, I
> am oaky too.
>
>
>>
>> I would also initialize the numa_node with NUMA_NO_NODE at declaration,
>> so that if someone calls cpu_to_node() before the variable is properly
>> initialized at runtime, he'll get NO_NODE, which is obviously an error.
>
> Even we set the numa_node with NUMA_NO_NODE, it does not always
> produce error.
>
> Please see the alloc_pages_node().
>
>
> Thanks
>
> Huang Shijie
>
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