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Commit 396ae57e authored by Kimberly Brown's avatar Kimberly Brown Committed by Sasha Levin
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Drivers: hv: vmbus: Expose counters for interrupts and full conditions 



Counter values for per-channel interrupts and ring buffer full
conditions are useful for investigating performance.

Expose counters in sysfs for 2 types of guest to host interrupts:
1) Interrupts caused by the channel's outbound ring buffer transitioning
from empty to not empty
2) Interrupts caused by the channel's inbound ring buffer transitioning
from full to not full while a packet is waiting for enough buffer space to
become available

Expose 2 counters in sysfs for the number of times that write operations
encountered a full outbound ring buffer:
1) The total number of write operations that encountered a full
condition
2) The number of write operations that were the first to encounter a
full condition

Increment the outbound full condition counters in the
hv_ringbuffer_write() function because, for most drivers, a full
outbound ring buffer is detected in that function. Also increment the
outbound full condition counters in the set_channel_pending_send_size()
function. In the hv_sock driver, a full outbound ring buffer is detected
and set_channel_pending_send_size() is called before
hv_ringbuffer_write() is called.

I tested this patch by confirming that the sysfs files were created and
observing the counter values. The values seemed to increase by a
reasonable amount when the Hyper-v related drivers were in use.

Signed-off-by: default avatarKimberly Brown <kimbrownkd@gmail.com>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 593db803

Documentation/ABI/stable/sysfs-bus-vmbus

+33 −0
Original line number Diff line number Diff line
@@ -146,3 +146,36 @@ KernelVersion: 4.16 
Contact:	Stephen Hemminger <sthemmin@microsoft.com>

Description:	Binary file created by uio_hv_generic for ring buffer

Users:		Userspace drivers



What:           /sys/bus/vmbus/devices/<UUID>/channels/<N>/intr_in_full

Date:           February 2019

KernelVersion:  5.0

Contact:        Michael Kelley <mikelley@microsoft.com>

Description:    Number of guest to host interrupts caused by the inbound ring

		buffer transitioning from full to not full while a packet is

		waiting for buffer space to become available

Users:          Debugging tools



What:           /sys/bus/vmbus/devices/<UUID>/channels/<N>/intr_out_empty

Date:           February 2019

KernelVersion:  5.0

Contact:        Michael Kelley <mikelley@microsoft.com>

Description:    Number of guest to host interrupts caused by the outbound ring

		buffer transitioning from empty to not empty

Users:          Debugging tools



What:           /sys/bus/vmbus/devices/<UUID>/channels/<N>/out_full_first

Date:           February 2019

KernelVersion:  5.0

Contact:        Michael Kelley <mikelley@microsoft.com>

Description:    Number of write operations that were the first to encounter an

		outbound ring buffer full condition

Users:          Debugging tools



What:           /sys/bus/vmbus/devices/<UUID>/channels/<N>/out_full_total

Date:           February 2019

KernelVersion:  5.0

Contact:        Michael Kelley <mikelley@microsoft.com>

Description:    Total number of write operations that encountered an outbound

		ring buffer full condition

Users:          Debugging tools

drivers/hv/ring_buffer.c

+13 −1
Original line number Diff line number Diff line
@@ -74,9 +74,11 @@ static void hv_signal_on_write(u32 old_write, struct vmbus_channel *channel) 
	 * This is the only case we need to signal when the

	 * ring transitions from being empty to non-empty.

	 */

	if (old_write == READ_ONCE(rbi->ring_buffer->read_index))

	if (old_write == READ_ONCE(rbi->ring_buffer->read_index)) {

		++channel->intr_out_empty;

		vmbus_setevent(channel);

	}

}



/* Get the next write location for the specified ring buffer. */

static inline u32
@@ -272,10 +274,19 @@ int hv_ringbuffer_write(struct vmbus_channel *channel, 
	 * is empty since the read index == write index.

	 */

	if (bytes_avail_towrite <= totalbytes_towrite) {

		++channel->out_full_total;



		if (!channel->out_full_flag) {

			++channel->out_full_first;

			channel->out_full_flag = true;

		}



		spin_unlock_irqrestore(&outring_info->ring_lock, flags);

		return -EAGAIN;

	}



	channel->out_full_flag = false;



	/* Write to the ring buffer */

	next_write_location = hv_get_next_write_location(outring_info);
@@ -530,6 +541,7 @@ void hv_pkt_iter_close(struct vmbus_channel *channel) 
	if (curr_write_sz <= pending_sz)

		return;



	++channel->intr_in_full;

	vmbus_setevent(channel);

}

EXPORT_SYMBOL_GPL(hv_pkt_iter_close);

drivers/hv/vmbus_drv.c

+36 −0
Original line number Diff line number Diff line
@@ -1484,6 +1484,38 @@ static ssize_t channel_events_show(const struct vmbus_channel *channel, char *bu 
}

static VMBUS_CHAN_ATTR(events, S_IRUGO, channel_events_show, NULL);



static ssize_t channel_intr_in_full_show(const struct vmbus_channel *channel,

					 char *buf)

{

	return sprintf(buf, "%llu\n",

		       (unsigned long long)channel->intr_in_full);

}

static VMBUS_CHAN_ATTR(intr_in_full, 0444, channel_intr_in_full_show, NULL);



static ssize_t channel_intr_out_empty_show(const struct vmbus_channel *channel,

					   char *buf)

{

	return sprintf(buf, "%llu\n",

		       (unsigned long long)channel->intr_out_empty);

}

static VMBUS_CHAN_ATTR(intr_out_empty, 0444, channel_intr_out_empty_show, NULL);



static ssize_t channel_out_full_first_show(const struct vmbus_channel *channel,

					   char *buf)

{

	return sprintf(buf, "%llu\n",

		       (unsigned long long)channel->out_full_first);

}

static VMBUS_CHAN_ATTR(out_full_first, 0444, channel_out_full_first_show, NULL);



static ssize_t channel_out_full_total_show(const struct vmbus_channel *channel,

					   char *buf)

{

	return sprintf(buf, "%llu\n",

		       (unsigned long long)channel->out_full_total);

}

static VMBUS_CHAN_ATTR(out_full_total, 0444, channel_out_full_total_show, NULL);



static ssize_t subchannel_monitor_id_show(const struct vmbus_channel *channel,

					  char *buf)

{
@@ -1509,6 +1541,10 @@ static struct attribute *vmbus_chan_attrs[] = { 
	&chan_attr_latency.attr,

	&chan_attr_interrupts.attr,

	&chan_attr_events.attr,

	&chan_attr_intr_in_full.attr,

	&chan_attr_intr_out_empty.attr,

	&chan_attr_out_full_first.attr,

	&chan_attr_out_full_total.attr,

	&chan_attr_monitor_id.attr,

	&chan_attr_subchannel_id.attr,

	NULL

include/linux/hyperv.h

+46 −0
Original line number Diff line number Diff line
@@ -751,6 +751,19 @@ struct vmbus_channel { 
	u64	interrupts;	/* Host to Guest interrupts */

	u64	sig_events;	/* Guest to Host events */



	/*

	 * Guest to host interrupts caused by the outbound ring buffer changing

	 * from empty to not empty.

	 */

	u64 intr_out_empty;



	/*

	 * Indicates that a full outbound ring buffer was encountered. The flag

	 * is set to true when a full outbound ring buffer is encountered and

	 * set to false when a write to the outbound ring buffer is completed.

	 */

	bool out_full_flag;



	/* Channel callback's invoked in softirq context */

	struct tasklet_struct callback_event;

	void (*onchannel_callback)(void *context);
@@ -903,6 +916,24 @@ struct vmbus_channel { 
	 * vmbus_connection.work_queue and hang: see vmbus_process_offer().

	 */

	struct work_struct add_channel_work;



	/*

	 * Guest to host interrupts caused by the inbound ring buffer changing

	 * from full to not full while a packet is waiting.

	 */

	u64 intr_in_full;



	/*

	 * The total number of write operations that encountered a full

	 * outbound ring buffer.

	 */

	u64 out_full_total;



	/*

	 * The number of write operations that were the first to encounter a

	 * full outbound ring buffer.

	 */

	u64 out_full_first;

};



static inline bool is_hvsock_channel(const struct vmbus_channel *c)
@@ -936,6 +967,21 @@ static inline void *get_per_channel_state(struct vmbus_channel *c) 
static inline void set_channel_pending_send_size(struct vmbus_channel *c,

						 u32 size)

{

	unsigned long flags;



	if (size) {

		spin_lock_irqsave(&c->outbound.ring_lock, flags);

		++c->out_full_total;



		if (!c->out_full_flag) {

			++c->out_full_first;

			c->out_full_flag = true;

		}

		spin_unlock_irqrestore(&c->outbound.ring_lock, flags);

	} else {

		c->out_full_flag = false;

	}



	c->outbound.ring_buffer->pending_send_sz = size;

}