Subject: Re: hackbench regression due to commit 9dfc6e68bfe6e

From: Pekka Enberg <[email-masked]>
Date: Wed, 07 Apr 2010 13:47:37 +0300

Zhang, Yanmin kirjoitti:
> Kernel 2.6.34-rc3:
> # Samples: 13079611308 LLC-load-misses
> #
> # Overhead          Command                                                         Shared Object  Symbol
> # ........  ...............  ....................................................................  ......
> #
>     18.55%        hackbench  [kernel.kallsyms]                                                     [k] copy_user_generic_str
> ing
>     13.19%        hackbench  [kernel.kallsyms]                                                     [k] unix_stream_recvmsg
>     11.62%        hackbench  [kernel.kallsyms]                                                     [k] kfree
>      8.54%        hackbench  [kernel.kallsyms]                                                     [k] kmem_cache_free
>      7.88%        hackbench  [kernel.kallsyms]                                                     [k] __kmalloc_node_track_
> caller
>      6.54%        hackbench  [kernel.kallsyms]                                                     [k] kmem_cache_alloc_node
>      5.94%        hackbench  [kernel.kallsyms]                                                     [k] kfree_skb
>      3.48%        hackbench  [kernel.kallsyms]                                                     [k] __slab_free
>      2.15%        hackbench  [kernel.kallsyms]                                                     [k] _raw_spin_lock
>      1.83%        hackbench  [kernel.kallsyms]                                                     [k] schedule
>      1.82%        hackbench  [kernel.kallsyms]                                                     [k] get_partial_node
>      1.59%        hackbench  hackbench                                                             [.] receiver
>      1.37%        hackbench  libpthread-2.9.so                                                     [.] __read

Btw, you might want to try out "perf record -g" and "perf report 
--callchain fractal,5" to get a better view of where we're spending 
time. Perhaps you can spot the difference with that more easily.