This is now under development patch (and I can't guarantee this is free from bug.)
The idea is coalescing multiple css_get/put to __css_get(),__css_put() as
we now do in res_counter charging.
Here is a result with multi-threaded page fault program. The program does continuous
page fault in 60 sec. If the kernel works better, we can see more page faults.
Here is a test result under a memcg(not root cgroup).
[before Patch]
[root@bluextal test]# /root/bin/perf stat -e page-faults,cache-misses ./multi-fault-all-split 8
Performance counter stats for './multi-fault-all-split 8':
12357708 page-faults
161332057 cache-misses
60.007931275 seconds time elapsed
25.31% multi-fault-all [kernel.kallsyms] [k] clear_page_c
9.24% multi-fault-all [kernel.kallsyms] [k] down_read_trylock
8.37% multi-fault-all [kernel.kallsyms] [k] try_get_mem_cgroup_from_mm
5.21% multi-fault-all [kernel.kallsyms] [k] __alloc_pages_nodemask
5.13% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irqsave
4.91% multi-fault-all [kernel.kallsyms] [k] __css_put
4.66% multi-fault-all [kernel.kallsyms] [k] up_read
3.17% multi-fault-all [kernel.kallsyms] [k] css_put
2.77% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irq
2.58% multi-fault-all [kernel.kallsyms] [k] page_fault
[after Patch]
[root@bluextal test]# /root/bin/perf stat -e page-faults,cache-misses ./multi-fault-all-split 8
Performance counter stats for './multi-fault-all-split 8':
13615258 page-faults
153207110 cache-misses
60.004117823 seconds time elapsed
# Overhead Command Shared Object Symbol
# ........ ............... ..................... ......
#
27.70% multi-fault-all [kernel.kallsyms] [k] clear_page_c
11.18% multi-fault-all [kernel.kallsyms] [k] down_read_trylock
7.54% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irqsave
5.99% multi-fault-all [kernel.kallsyms] [k] up_read
5.90% multi-fault-all [kernel.kallsyms] [k] __alloc_pages_nodemask
5.13% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irq
2.73% multi-fault-all [kernel.kallsyms] [k] __mem_cgroup_commit_charge
2.71% multi-fault-all [kernel.kallsyms] [k] page_fault
2.66% multi-fault-all [kernel.kallsyms] [k] handle_mm_fault
2.35% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock
You can see cache-miss/page-faults is improved and no css_get/css_put in overhead
stat record. Please give me your review if interested.
(I tried to get rid of css_get()/put() per a page ...but..it seems no very easy.
So, now trying to reduce overheads.)
Thanks,
-Kame
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