blktrace vs ftrace

[Matthias Brugger]

Hi,

On 02/03/2012 06:59 AM, Mulyadi Santosa wrote:
>
> I could only offer this explanation:
> blktrace traces events in block level. In this level, I/O is likely
> serialized....unless you have more than one physical disks.
>
> in ftrace, you see events right before it hits block level operation.
> Somewhere between VFS, filesystem operation and I/O scheduling which
> deals with queue reordering. In this case, parallel operation is
> likely to happen because more than processes could submit read or
> write.

If I understand the patch which introduces the blk tracer to ftrace 
(http://lwn.net/Articles/315508/) just uses the blktrace interface. So I 
wonder why using this influences the I/O behaviour.

Best regards,
Matthias