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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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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

Anton.



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