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Commit 13882a82 authored by Clemens Ladisch's avatar Clemens Ladisch Committed by Stefan Richter
Browse files

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: default avatarClemens Ladisch <clemens@ladisch.de>
Signed-off-by: default avatarStefan Richter <stefanr@s5r6.in-berlin.de>
parent f30e6d3e

drivers/firewire/core-card.c

+5 −0
Original line number Diff line number Diff line
@@ -630,6 +630,10 @@ static int dummy_queue_iso(struct fw_iso_context *ctx, struct fw_iso_packet *p, 
	return -ENODEV;

}



static void dummy_flush_queue_iso(struct fw_iso_context *ctx)

{

}



static const struct fw_card_driver dummy_driver_template = {

	.read_phy_reg		= dummy_read_phy_reg,

	.update_phy_reg		= dummy_update_phy_reg,
@@ -641,6 +645,7 @@ static const struct fw_card_driver dummy_driver_template = { 
	.start_iso		= dummy_start_iso,

	.set_iso_channels	= dummy_set_iso_channels,

	.queue_iso		= dummy_queue_iso,

	.flush_queue_iso	= dummy_flush_queue_iso,

};



void fw_card_release(struct kref *kref)

drivers/firewire/core-cdev.c

+1 −0
Original line number Diff line number Diff line
@@ -1107,6 +1107,7 @@ static int ioctl_queue_iso(struct client *client, union ioctl_arg *arg) 
		payload += u.packet.payload_length;

		count++;

	}

	fw_iso_context_queue_flush(ctx);



	a->size    -= uptr_to_u64(p) - a->packets;

	a->packets  = uptr_to_u64(p);

drivers/firewire/core-iso.c

+6 −0
Original line number Diff line number Diff line
@@ -185,6 +185,12 @@ int fw_iso_context_queue(struct fw_iso_context *ctx, 
}

EXPORT_SYMBOL(fw_iso_context_queue);



void fw_iso_context_queue_flush(struct fw_iso_context *ctx)

{

	ctx->card->driver->flush_queue_iso(ctx);

}

EXPORT_SYMBOL(fw_iso_context_queue_flush);



int fw_iso_context_stop(struct fw_iso_context *ctx)

{

	return ctx->card->driver->stop_iso(ctx);

drivers/firewire/core.h

+2 −0
Original line number Diff line number Diff line
@@ -97,6 +97,8 @@ struct fw_card_driver { 
			 struct fw_iso_buffer *buffer,

			 unsigned long payload);



	void (*flush_queue_iso)(struct fw_iso_context *ctx);



	int (*stop_iso)(struct fw_iso_context *ctx);

};

drivers/firewire/net.c

+3 −1
Original line number Diff line number Diff line
@@ -881,7 +881,9 @@ static void fwnet_receive_broadcast(struct fw_iso_context *context, 


	spin_unlock_irqrestore(&dev->lock, flags);



	if (retval < 0)

	if (retval >= 0)

		fw_iso_context_queue_flush(dev->broadcast_rcv_context);

	else

		fw_error("requeue failed\n");

}