Commit 78c65f0f authored by Saurabh Sengar's avatar Saurabh Sengar Committed by Wei Liu
Browse files

Drivers: hv: vmbus: Optimize vmbus_on_event 



In the vmbus_on_event loop, 2 jiffies timer will not serve the purpose if
callback_fn takes longer. For effective use move this check inside of
callback functions where needed. Out of all the VMbus drivers using
vmbus_on_event, only storvsc has a high packet volume, thus add this limit
only in storvsc callback for now.
There is no apparent benefit of loop itself because this tasklet will be
scheduled anyway again if there are packets left in ring buffer. This
patch removes this unnecessary loop as well.

Signed-off-by: default avatarSaurabh Sengar <ssengar@linux.microsoft.com>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1658741848-4210-1-git-send-email-ssengar@linux.microsoft.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
parent 521a547c

drivers/hv/connection.c

+14 −19
Original line number Diff line number Diff line
@@ -431,20 +431,18 @@ struct vmbus_channel *relid2channel(u32 relid) 
void vmbus_on_event(unsigned long data)

{

	struct vmbus_channel *channel = (void *) data;

	unsigned long time_limit = jiffies + 2;

	void (*callback_fn)(void *context);



	trace_vmbus_on_event(channel);



	hv_debug_delay_test(channel, INTERRUPT_DELAY);

	do {

		void (*callback_fn)(void *);



	/* A channel once created is persistent even when

	 * there is no driver handling the device. An

	 * unloading driver sets the onchannel_callback to NULL.

	 */

	callback_fn = READ_ONCE(channel->onchannel_callback);

		if (unlikely(callback_fn == NULL))

	if (unlikely(!callback_fn))

		return;



	(*callback_fn)(channel->channel_callback_context);
@@ -456,9 +454,6 @@ void vmbus_on_event(unsigned long data) 
		return;



	hv_begin_read(&channel->inbound);

	} while (likely(time_before(jiffies, time_limit)));



	/* The time limit (2 jiffies) has been reached */

	tasklet_schedule(&channel->callback_event);

}

drivers/scsi/storvsc_drv.c

+9 −0
Original line number Diff line number Diff line
@@ -60,6 +60,9 @@ 
#define VMSTOR_PROTO_VERSION_WIN8_1	VMSTOR_PROTO_VERSION(6, 0)

#define VMSTOR_PROTO_VERSION_WIN10	VMSTOR_PROTO_VERSION(6, 2)



/* channel callback timeout in ms */

#define CALLBACK_TIMEOUT               2



/*  Packet structure describing virtual storage requests. */

enum vstor_packet_operation {

	VSTOR_OPERATION_COMPLETE_IO		= 1,
@@ -1204,6 +1207,7 @@ static void storvsc_on_channel_callback(void *context) 
	struct hv_device *device;

	struct storvsc_device *stor_device;

	struct Scsi_Host *shost;

	unsigned long time_limit = jiffies + msecs_to_jiffies(CALLBACK_TIMEOUT);



	if (channel->primary_channel != NULL)

		device = channel->primary_channel->device_obj;
@@ -1224,6 +1228,11 @@ static void storvsc_on_channel_callback(void *context) 
		u32 minlen = rqst_id ? sizeof(struct vstor_packet) :

			sizeof(enum vstor_packet_operation);



		if (unlikely(time_after(jiffies, time_limit))) {

			hv_pkt_iter_close(channel);

			return;

		}



		if (pktlen < minlen) {

			dev_err(&device->device,

				"Invalid pkt: id=%llu, len=%u, minlen=%u\n",