[PATCH] NUMA: Early use of cpu_to_node() returns 0 instead of the correct node id
Mike Rapoport
rppt at kernel.org
Fri Jan 19 00:42:04 PST 2024
On Fri, Jan 19, 2024 at 02:46:16PM +0800, Shijie Huang wrote:
>
> 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%
It's not only about text size, the indirect call also hurts performance
> >
> > 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.
> >
> > 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.
Is there a fundamental reason to have early_cpu_to_node() at all?
It seems that all the mappings are known by the end of setup_arch() and the
initialization of numa_node can be moved earlier.
> > 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
>
--
Sincerely yours,
Mike.
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