Re: REGRESSION: Performance regressions from switching anon_vma->lock to mutex
From: Tim Chen <hidden>
Date: 2011-06-17 18:22:18
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On Thu, 2011-06-16 at 20:58 -0700, Linus Torvalds wrote:
So Tim, I'd like you to test out my first patch (that only does the
anon_vma_clone() case) once again, but now in the cleaned-up version.
Does this patch really make a big improvement for you? If so, this
first step is probably worth doing regardless of the more complicated
second step, but I'd want to really make sure it's ok, and that the
performance improvement you saw is consistent and not a fluke.
Linus
Linus,
For this patch, I've run it 10 times and got an average throughput of
104.9% compared with 2.6.39 vanilla baseline. Wide variations are seen
run to run and the difference between max and min throughput is 52% of
average value.
So to recap,
Throughput
2.6.39(vanilla) 100.0%
2.6.39+ra-patch 166.7% (+66.7%)
3.0-rc2(vanilla) 68.0% (-32%)
3.0-rc2+linus 115.7% (+15.7%)
3.0-rc2+linus+softirq 86.2% (-17.3%)
3.0-rc2+linus (v2) 104.9% (+4.9%)
The time spent in the anon_vma mutex seems to directly affect
throughput.
In one run on your patch, I got a low throughput of 90.1% vs 2.6.39
throughput. The mutex_lock occupied 15.6% of cpu.
In another run, I got a high throughput of 120.8% vs 2.6.39 throughput.
The mutex lock occupied 7.5% of cpu.
I've attached the profiles of the two runs and a 3.0-rc2 vanilla run for
your reference.
I will follow up later with numbers that has Peter's patch added.
Thanks.
Tim
----------Profiles Below-------------------------
3.0-rc2+linus(v2) run 1 (90.1% throughput vs 2.6.39)
- 15.60% exim [kernel.kallsyms] [k] __mutex_lock_common.clone.5
- __mutex_lock_common.clone.5
- 99.99% __mutex_lock_slowpath
- mutex_lock
+ 75.52% anon_vma_lock.clone.10
+ 23.88% anon_vma_clone
- 4.38% exim [kernel.kallsyms] [k] _raw_spin_lock_irqsave
- _raw_spin_lock_irqsave
+ 82.83% cpupri_set
+ 6.75% try_to_wake_up
+ 5.35% release_pages
+ 1.72% pagevec_lru_move_fn
+ 0.93% get_page_from_freelist
+ 0.51% lock_timer_base.clone.20
+ 3.22% exim [kernel.kallsyms] [k] page_fault
+ 2.62% exim [kernel.kallsyms] [k] do_raw_spin_lock
+ 2.30% exim [kernel.kallsyms] [k] mutex_unlock
+ 2.02% exim [kernel.kallsyms] [k] unmap_vmas
3.0-rc2_linus(v2) run 2 (120.8% throughput vs 2.6.39)
- 7.53% exim [kernel.kallsyms] [k] __mutex_lock_common.clone.5
- __mutex_lock_common.clone.5
- 99.99% __mutex_lock_slowpath
- mutex_lock
+ 75.99% anon_vma_lock.clone.10
+ 22.68% anon_vma_clone
+ 0.70% unlink_file_vma
- 4.15% exim [kernel.kallsyms] [k] _raw_spin_lock_irqsave
- _raw_spin_lock_irqsave
+ 83.37% cpupri_set
+ 7.06% release_pages
+ 2.74% pagevec_lru_move_fn
+ 2.18% try_to_wake_up
+ 0.99% get_page_from_freelist
+ 0.59% lock_timer_base.clone.20
+ 0.58% lock_hrtimer_base.clone.16
+ 4.06% exim [kernel.kallsyms] [k] page_fault
+ 2.33% exim [kernel.kallsyms] [k] unmap_vmas
+ 2.22% exim [kernel.kallsyms] [k] do_raw_spin_lock
+ 2.05% exim [kernel.kallsyms] [k] page_cache_get_speculative
+ 1.98% exim [kernel.kallsyms] [k] mutex_unlock
3.0-rc2 vanilla run
- 18.60% exim [kernel.kallsyms] [k] __mutex_lock_common.clone.5 a??
- __mutex_lock_common.clone.5 a?(R)
- 99.99% __mutex_lock_slowpath a??
- mutex_lock a??
- 99.54% anon_vma_lock.clone.10 a??
+ 38.99% anon_vma_clone a??
+ 37.56% unlink_anon_vmas a??
+ 11.92% anon_vma_fork a??
+ 11.53% anon_vma_free a??
- 4.03% exim [kernel.kallsyms] [k] _raw_spin_lock_irqsave a??
- _raw_spin_lock_irqsave a??
+ 87.25% cpupri_set a??
+ 4.75% release_pages a??
+ 3.68% try_to_wake_up a??
+ 1.17% pagevec_lru_move_fn a??
+ 0.71% get_page_from_freelist a??
+ 3.00% exim [kernel.kallsyms] [k] do_raw_spin_lock a??
+ 2.90% exim [kernel.kallsyms] [k] page_fault a??
+ 2.25% exim [kernel.kallsyms] [k] mutex_unlock a??
+ 1.82% exim [kernel.kallsyms] [k] unmap_vmas a??
+ 1.62% exim [kernel.kallsyms] [k] copy_page_c a??
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