Re: Raw I/O enhancements for 2.3.99.pre9-2 kernels.

[Chaitanya Tumuluri <chait@xxxxxxxxxxxxxxxxxxxx>]

On Thu, 08 Jun 2000 10:25:36 PDT, "Matt D. Robinson" <yakker@xxxxxxxxxxxxxx> 
wrote:
>On Fri, 26 May 2000, Chaitanya Tumuluri wrote:
>|>Hey Matt! What kind of problems and which kernel are you talking
>|>about? D'ju have any particular testcase I could use?
>
>I got it to work ... the deal is not to use map_kernel_kiobuf() for
>the stuff I'm doing.  It's better just to do something like:

Cool. Thats good to know. What was the problem you had with 
map_kernel_kiobuf() anyways?

Question: Do you take care not to alloc from highmem, to avoid
          bouncing?
>
>       /* do brw_kiovec on the kiobuf here */
>

Why brw_kiovec? That would send you into the buffer-head path and slow
you down by as much as 40%. Why not the rawio path (i.e. try_kiobuf_io()
in drivers/char/raw.c)?

Cheers,
-Chait.