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Date:   Thu, 17 Jan 2019 06:45:14 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     kimbrownkd <kimbrownkd@...il.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Long Li <longli@...rosoft.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3] Drivers: hv: vmbus: Expose counters for interrupts and
 full conditions

> From: Kimberly Brown <kimbrownkd@...il.com>
> Sent: Wednesday, January 16, 2019 8:38 PM
> To: Michael Kelley <mikelley@...rosoft.com>; Long Li
> <longli@...rosoft.com>; Sasha Levin <Alexander.Levin@...rosoft.com>;
> Dexuan Cui <decui@...rosoft.com>
> Cc: KY Srinivasan <kys@...rosoft.com>; Haiyang Zhang
> <haiyangz@...rosoft.com>; Stephen Hemminger
> <sthemmin@...rosoft.com>; devel@...uxdriverproject.org;
> linux-kernel@...r.kernel.org
> Subject: [PATCH v3] 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
> 
> 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 <kimbrownkd@...il.com>
> ---
> Changes in v3:
>  - Used the outbound ring buffer spinlock to protect the the full
>    condition counters in set_channel_pending_send_size()
>  - Corrected the KernelVersion values for the new entries in
>    Documentation/ABI/stable/sysfs-bus-vmbus
> 
> Changes in v2:
>  - Added mailing lists to the cc list
>  - Removed the host to guest interrupt counters proposed in v1 because
>    they were not accurate
>  - Added full condition counters for the channel's outbound ring buffer
> 
>  Documentation/ABI/stable/sysfs-bus-vmbus | 33 ++++++++++++++++++++
>  drivers/hv/ring_buffer.c                 | 14 ++++++++-
>  drivers/hv/vmbus_drv.c                   | 32 ++++++++++++++++++++
>  include/linux/hyperv.h                   | 38
> ++++++++++++++++++++++++
>  4 files changed, 116 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/stable/sysfs-bus-vmbus
> b/Documentation/ABI/stable/sysfs-bus-vmbus
> index 3fed8fdb873d..a0304c563467 100644
> --- a/Documentation/ABI/stable/sysfs-bus-vmbus
> +++ b/Documentation/ABI/stable/sysfs-bus-vmbus
> @@ -146,3 +146,36 @@ KernelVersion:	4.16
>  Contact:	Stephen Hemminger <sthemmin@...rosoft.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:           January 2019
> +KernelVersion:  5.0
> +Contact:        Michael Kelley <mikelley@...rosoft.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:           January 2019
> +KernelVersion:  5.0
> +Contact:        Michael Kelley <mikelley@...rosoft.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:           January 2019
> +KernelVersion:  5.0
> +Contact:        Michael Kelley <mikelley@...rosoft.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:           January 2019
> +KernelVersion:  5.0
> +Contact:        Michael Kelley <mikelley@...rosoft.com>
> +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 1f1a55e07733..9e8b31ccc142 100644
> --- 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 403fee01572c..e291a7d3180c 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -1496,6 +1496,34 @@ 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", 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", 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", 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", 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)
>  {
> @@ -1521,6 +1549,10 @@ 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 dcb6977afce9..7e5239123276 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -751,6 +751,27 @@ struct vmbus_channel {
>  	u64	interrupts;	/* Host to Guest interrupts */
>  	u64	sig_events;	/* Guest to Host events */
> 
> +	/* Interrupt counts for 2 types of Guest to Host interrupts */
> +	u64 intr_in_full;	/* in ring buffer, full to not full */
> +	u64 intr_out_empty;	/* out ring buffer, empty to not empty */
> +
> +	/*
> +	 * 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;
> +	/*
> +	 * 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);
> @@ -936,6 +957,23 @@ 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;
> +
> +	spin_lock_irqsave(&c->outbound.ring_lock, flags);
> +
> +	if (size) {
> +		++c->out_full_total;
> +
> +		if (!c->out_full_flag) {
> +			++c->out_full_first;
> +			c->out_full_flag = true;
> +		}
> +	} else {
> +		c->out_full_flag = false;
> +	}
> +
> +	spin_unlock_irqrestore(&c->outbound.ring_lock, flags);
> +
>  	c->outbound.ring_buffer->pending_send_sz = size;
>  }
> 
> --
> 2.17.1

Looks good to me. 

Reviewed-by: Dexuan Cui <decui@...rosoft.com>

-- Dexuan

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