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: Kimberly Brown <[email protected]>
Reviewed-by:  Michael Kelley <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

diff --git a/Documentation/ABI/stable/sysfs-bus-vmbus b/Documentation/ABI/stable/sysfs-bus-vmbus
index 3fed8fdb873d723e3bc25e155dee3be2d797d352..826689dcc2e67370102d73eae9c359e9547df710 100644 (file)
--- a/Documentation/ABI/stable/sysfs-bus-vmbus
+++ b/Documentation/ABI/stable/sysfs-bus-vmbus
@@ -146,3 +146,36 @@ KernelVersion:     4.16
 Contact:       Stephen Hemminger <[email protected]>
 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 <[email protected]>
+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 <[email protected]>
+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 <[email protected]>
+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 <[email protected]>
+Description:    Total number of write operations that encountered an outbound
+               ring buffer full condition
+Users:          Debugging tools

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 1f1a55e077338cabf233bba7630d805f84fd96f6..9e8b31ccc14262a736f11109d6021c621d9d453e 100644 (file)
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -74,8 +74,10 @@ 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. */
@@ -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);

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 126c2de39e3564714bd1761b75146fdf89563508..1264b17e7e9d860e53727321bbcd8b42225792d3 100644 (file)
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -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

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index d5678a0fe59866ec013b8fdb363aaa75a53b8846..64698ec8f2accd3d3e939f61a9f860623cd6d3ca 100644 (file)
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -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;
 }