[Samba] Samba write performance in kernel

[Scott Lovenberg]

Lin Mac wrote:
> hi,
>
> I would like to know is it possible to make writing file to samba completely in kernel?
>
> I'm using a slow CPU (FA526) , and the memory copy is even slower. The reading performance is over 7 MB/s, with mmap and sendfile enabled, while writing is only 4-5 MB/s. Without mmap and sendfile, reading from samba is also about 4-5 MB/s. I use Oprofile to profile writing file to samba and found that CPU takes over 30% CPU time on copy_from/to_user, so I think going to user space and back again is the bottleneck.
>
> Since there is sendfile, why is'nt there counterpart on write path? Is there some difficalties or what? Is it implementable?
>
> Please give me some advice.
>
>
> Best Regards,
> Mac Lin
>
>   
Are you using DMA, or are you copying byte by byte through the CPU?