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SubjectRe: [Bugme-new] [Bug 15618] New: 2.6.18->2.6.32->2.6.33 huge regression in performance
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I attach here callgraph.

Also I checked kernel source, actual code which was compiled is exactly what should be after patches.

Do I miss something?

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On Mar 23, 2010, at 8:17 PM, Peter Zijlstra wrote:

> On Tue, 2010-03-23 at 20:14 +0100, Anton Starikov wrote:
>> On Mar 23, 2010, at 6:45 PM, Linus Torvalds wrote:
>>
>>>
>>>
>>> On Tue, 23 Mar 2010, Ingo Molnar wrote:
>>>>
>>>> It shows a very brutal amount of page fault invoked mmap_sem spinning
>>>> overhead.
>>>
>>> Isn't this already fixed? It's the same old "x86-64 rwsemaphores are using
>>> the shit-for-brains generic version" thing, and it's fixed by
>>>
>>> 1838ef1 x86-64, rwsem: 64-bit xadd rwsem implementation
>>> 5d0b723 x86: clean up rwsem type system
>>> 59c33fa x86-32: clean up rwsem inline asm statements
>>>
>>> NOTE! None of those are in 2.6.33 - they were merged afterwards. But they
>>> are in 2.6.34-rc1 (and obviously current -git). So Anton would have to
>>> compile his own kernel to test his load.
>>
>>
>> Applied mentioned patches. Things didn't improve too much.
>>
>> before:
>> prog: Total exploration time 9.880 real 60.620 user 76.970 sys
>>
>> after:
>> prog: Total exploration time 9.020 real 59.430 user 66.190 sys
>>
>> perf report:
>>
>> 38.58% prog [kernel] [k] _spin_lock_irqsave
>> 37.42% prog ./prog [.] DBSLLlookup_ret
>> 6.22% prog ./prog [.] SuperFastHash
>> 3.65% prog /lib64/libc-2.11.1.so [.] __GI_memcpy
>> 2.09% prog ./anderson.6.dve2C [.] get_successors
>> 1.75% prog [kernel] [k] clear_page_c
>> 1.73% prog ./prog [.] index_next_dfs
>> 0.71% prog [kernel] [k] handle_mm_fault
>> 0.38% prog ./prog [.] cb_hook
>> 0.33% prog ./prog [.] get_local
>> 0.32% prog [kernel] [k] page_fault
>
> Could you verify with a callgraph profile what that spin_lock_irqsave()
> is? If those rwsem patches were successfull mmap_sem should no longer
> have a spinlock to content on, in which case it might be another lock.
>
> If not, something went wrong with backporting those patches.

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