在 2024/1/20 2:02, Yury Norov 写道:
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On Fri, Jan 19, 2024 at 04:50:53PM +0800, Shijie Huang wrote:
在 2024/1/19 16:42, Mike Rapoport 写道:
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
The cpu_to_node() is called at very low frequency, most of the times is in
the kernel booting time.
That doesn't matter. This function is a simple inliner that dereferences
a pointer, and I believe all of us want to keep it simple.
Yes. I agree.
I also want to keep it simple too.
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?
The early_cpu_to_node does not work on some ARCHs (which support the NUMA),
such
as SPARC, MIPS and S390.
So, your approach wouldn't work either, right? I think you've got a
testing bot report on it already...
IMHO, my patch works fine for them.
They have their own cpu_to_node.
The x86 reported an compiling error, because the x86 does not compile
the driver/base/arch_numa.c.
I have fixed it by moving the cpu_to_node from
driver/base/arch_numa.c to driver/base/node.c
The driver/base/node.c is built-in for all the NUMA ARCHs.
You can make it like this:
#ifdef CONFIG_ARCH_NO_EARLY_CPU_TO_NODE
#define early_cpu_to_node cpu_to_node
#endif
Thanks. Add this make it more complicated..
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.
You can print this error yourself:
#ifndef cpu_to_node
static inline int cpu_to_node(int cpu)
{
int node = per_cpu(numa_node, cpu);
#ifdef CONFIG_DEBUG_PER_CPU_MAPS
if (node == NUMA_NO_NODE)
pr_err(...);
#endif
return node;
}
#endif
Thanks. I had a samiliar private to detect it.
After my patch, there is no need to detect the error again.
Thanks
Huang Shijie
