[dm-devel] [PATCH v2 7/7] dm snapshot: use bufio prefetch
Mikulas Patocka
mpatocka at redhat.com
Mon Jan 13 23:45:30 UTC 2014
On Mon, 13 Jan 2014, Mike Snitzer wrote:
> On Mon, Jan 13 2014 at 5:00pm -0500,
> Mikulas Patocka <mpatocka at redhat.com> wrote:
>
> > No.
> >
> > This changed patch inefficiently loops in bufio_prefetch_chunks for each
> > buffer that is read.
>
> Yeah, I overlooked the importance of preserving prefetch_area (which
> explains the unlikely you had). But my intent was to make your code
> less "special"; your if (DM_PREFETCH_CHUNKS) do { } while() code to
> avoid the extra indentation is pretty ugly.
>
> Given your current code, DM_PREFETCH_CHUNKS is always 12 so why not just
> remove the check?
If someone ever changes it to a variable, the condition is there avoid
unneeded call to dm_bufio_prefetch. The compiler optimizes out the
constant expression, so it doesn't matter that it's there.
Mikulas
More information about the dm-devel
mailing list