linux/drivers/media
Clemens Ladisch 13882a82ee firewire: optimize iso queueing by setting wake only after the last packet
When queueing iso packets, the run time is dominated by the two
MMIO accesses that set the DMA context's wake bit.  Because most
drivers submit packets in batches, we can save much time by
removing all but the last wakeup.

The internal kernel API is changed to require a call to
fw_iso_context_queue_flush() after a batch of queued packets.
The user space API does not change, so one call to
FW_CDEV_IOC_QUEUE_ISO must specify multiple packets to take
advantage of this optimization.

In my measurements, this patch reduces the time needed to queue
fifty skip packets from userspace to one sixth on a 2.5 GHz CPU,
or to one third at 800 MHz.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2011-05-10 22:53:45 +02:00
..
common Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6 2011-04-27 15:17:52 -07:00
dvb firewire: optimize iso queueing by setting wake only after the last packet 2011-05-10 22:53:45 +02:00
radio Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6 2011-05-04 14:22:04 -07:00
rc Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6 2011-05-04 14:22:04 -07:00
video Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6 2011-05-04 14:22:04 -07:00
Kconfig [media] v4l: Create v4l2 subdev file handle structure 2011-03-22 04:53:26 -03:00
Makefile [media] media: Entities, pads and links 2011-03-22 04:53:10 -03:00
media-device.c [media] media: Links setup 2011-03-22 04:53:16 -03:00
media-devnode.c [media] media: Media device node support 2011-03-22 04:52:22 -03:00
media-entity.c [media] media: Properly handle link flags in link setup, link notify callback 2011-04-17 07:43:32 -03:00