Pull percpu updates from Dennis Zhou:
"One bigger change to percpu_counter's api allowing for init and
destroy of multiple counters via percpu_counter_init_many() and
percpu_counter_destroy_many(). This is used to help begin remediating
a performance regression with percpu rss stats.
Additionally, it seems larger core count machines are feeling the
burden of the single threaded allocation of percpu. Mateusz is
thinking about it and I will spend some time on it too.
percpu:
- A couple cleanups by Baoquan He and Bibo Mao. The only behavior
change is to start printing messages if we're under the warn limit
for failed atomic allocations.
percpu_counter:
- Shakeel introduced percpu counters into mm_struct which caused
percpu allocations be on the hot path [1]. Originally I spent some
time trying to improve the percpu allocator, but instead preferred
what Mateusz Guzik proposed grouping at the allocation site,
percpu_counter_init_many(). This allows a single percpu allocation
to be shared by the counters. I like this approach because it
creates a shared lifetime by the allocations. Additionally, I
believe many inits have higher level synchronization requirements,
like percpu_counter does against HOTPLUG_CPU. Therefore we can
group these optimizations together"
Link: https://lore.kernel.org/linux-mm/20221024052841.3291983-1-shakeelb@google.com/
* tag 'percpu-for-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu:
kernel/fork: group allocation/free of per-cpu counters for mm struct
pcpcntr: add group allocation/free
mm/percpu.c: print error message too if atomic alloc failed
mm/percpu.c: optimize the code in pcpu_setup_first_chunk() a little bit
mm/percpu.c: remove redundant check
mm/percpu: Remove some local variables in pcpu_populate_pte
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