[Samba] Samba4 consumes more CPU

[Jeremy Allison]

On Mon, Sep 30, 2013 at 05:21:44PM -0300, Thiago Fernandes Crepaldi wrote:
> Andrew, in my company we are also experiencing a higher CPU usage of Samba
> 4 (smbd) if compared to Samba 3.
> 
> In fact, it almost reaches 100% of CPU and uses all the memory during *dir
> copies* (individual file copy is as good as samba 3's). I strongly believe
> that this CPU usage is the responsible for a worse samba 4's throughput if
> compared to Samba 3 tests.
> 
> Giving that, I would like to contribute with this investigation and share
> my data regarding perf profiling on smbd (parent process)
> 
> Events: 7  cycles
> -  90.01%  smbd  [kernel.kallsyms]  [k] copy_pte_range
>      copy_pte_range
>      __libc_fork
>      smbd_accept_connection
> -   9.77%  smbd  [kernel.kallsyms]  [k] handle_edge_irq
>      handle_edge_irq
>      smbd_accept_connection
> -   0.22%  smbd  [kernel.kallsyms]  [k] perf_pmu_rotate_start.isra.57
>      perf_pmu_rotate_start.isra.57
>      __poll
> -   0.00%  smbd  [kernel.kallsyms]  [k] native_write_msr_safe
>      native_write_msr_safe
>      __poll

It's the client process that should have the interesting
profile data, the parent is just going to sit there doing
accept().

Jeremy.