[Intel-gfx] [PATCH 14/17] drm/i915: Add stats for GuC log buffer flush interrupts

[Goel, Akash]

On 7/18/2016 3:46 PM, Tvrtko Ursulin wrote:
>
> On 15/07/16 16:58, Goel, Akash wrote:
>> On 7/15/2016 5:21 PM, Tvrtko Ursulin wrote:
>>> On 10/07/16 14:41, akash.goel at intel.com wrote:
>>>> From: Akash Goel <akash.goel at intel.com>
>>>>
>>>> GuC firmware sends an interrupt to flush the log buffer when it
>>>> becomes half full. GuC firmware also tracks how many times the
>>>> buffer overflowed.
>>>> It would be useful to maintain a statistics of how many flush
>>>> interrupts were received and for which type of log buffer,
>>>> along with the overflow count of each buffer type.
>>>> Augmented i915_log_info debugfs to report back these statistics.
>>>>
>>>> Signed-off-by: Akash Goel <akash.goel at intel.com>
>>>> ---
>>>>   drivers/gpu/drm/i915/i915_debugfs.c        | 26
>>>> ++++++++++++++++++++++++++
>>>>   drivers/gpu/drm/i915/i915_guc_submission.c |  8 ++++++++
>>>>   drivers/gpu/drm/i915/i915_irq.c            |  1 +
>>>>   drivers/gpu/drm/i915/intel_guc.h           |  6 ++++++
>>>>   4 files changed, 41 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c
>>>> b/drivers/gpu/drm/i915/i915_debugfs.c
>>>> index 3c9c7f7..888a18a 100644
>>>> --- a/drivers/gpu/drm/i915/i915_debugfs.c
>>>> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
>>>> @@ -2538,6 +2538,30 @@ static int i915_guc_load_status_info(struct
>>>> seq_file *m, void *data)
>>>>       return 0;
>>>>   }
>>>>
>>>> +static void i915_guc_log_info(struct seq_file *m,
>>>> +                 struct drm_i915_private *dev_priv)
>>>> +{
>>>> +    struct intel_guc *guc = &dev_priv->guc;
>>>> +
>>>> +    seq_printf(m, "\nGuC logging stats:\n");
>>>> +
>>>> +    seq_printf(m, "\tISR:   flush count %10u, overflow count %8u\n",
>>>> +        guc->log.flush_count[GUC_ISR_LOG_BUFFER],
>>>> +        guc->log.total_overflow_count[GUC_ISR_LOG_BUFFER]);
>>>> +
>>>> +    seq_printf(m, "\tDPC:   flush count %10u, overflow count %8u\n",
>>>> +        guc->log.flush_count[GUC_DPC_LOG_BUFFER],
>>>> +        guc->log.total_overflow_count[GUC_DPC_LOG_BUFFER]);
>>>> +
>>>> +    seq_printf(m, "\tCRASH: flush count %10u, overflow count %8u\n",
>>>> +        guc->log.flush_count[GUC_CRASH_DUMP_LOG_BUFFER],
>>>> +        guc->log.total_overflow_count[GUC_CRASH_DUMP_LOG_BUFFER]);
>>>> +
>>>> +    seq_printf(m, "\tTotal flush interrupt count: %u\n",
>>>> +            guc->log.flush_interrupt_count);
>>>> +
>>>> +}
>>>> +
>>>>   static void i915_guc_client_info(struct seq_file *m,
>>>>                    struct drm_i915_private *dev_priv,
>>>>                    struct i915_guc_client *client)
>>>> @@ -2611,6 +2635,8 @@ static int i915_guc_info(struct seq_file *m,
>>>> void *data)
>>>>       seq_printf(m, "\nGuC execbuf client @ %p:\n",
>>>> guc.execbuf_client);
>>>>       i915_guc_client_info(m, dev_priv, &client);
>>>>
>>>> +    i915_guc_log_info(m, dev_priv);
>>>> +
>>>>       /* Add more as required ... */
>>>>
>>>>       return 0;
>>>> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c
>>>> b/drivers/gpu/drm/i915/i915_guc_submission.c
>>>> index c1e637f..9c94a43 100644
>>>> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
>>>> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
>>>> @@ -914,6 +914,14 @@ static void guc_read_update_log_buffer(struct
>>>> drm_device *dev)
>>>>           log_buffer_state_local = *log_buffer_state;
>>>>           buffer_size = log_buffer_state_local.size;
>>>>
>>>> +        guc->log.flush_count[i] +=
>>>> log_buffer_state_local.flush_to_file;
>>>> +        if (log_buffer_state_local.buffer_full_cnt !=
>>>> +                    guc->log.prev_overflow_count[i]) {
>>>> +            guc->log.prev_overflow_count[i] =
>>>> +                    log_buffer_state_local.buffer_full_cnt;
>>>> +            guc->log.total_overflow_count[i]++;
>>>
>>> Is log_buffer_state_local.buffer_full_cnt guaranteed to be one here? Or
>>> you would need to increase total_overflow_count by its value?
>>>
>>
>> buffer_full_cnt will not remain as one. Its a 4 bit counter, will be
>> incremented monotonically by GuC firmware on every new detection of
>> overflow, so will increase from 0 to 15 & then wrap around.
>> Hence have to use '!=' in the condition instead of '>'.
>
> But can it happen that it jumps by more than one between being sampled
> here? In which case you would need to replace:
>
> guc->log.total_overflow_count[i]++;
>
> by something like:
>
>
> guc->log.total_overflow_count[i] +=
> log_buffer_state_local.buffer_full_cnt - guc->log.prev_overflow_count[i];
>
> (Doesn't handle the wrap though, just to illustrate my point.)
>
Actually logic in GuC firmware is such that overflow counter cannot 
increment by more than 1 without Driver coming into picture in between, 
by the virtue of flush interrupt.
But nevertheless the logic on Driver side should be like the way you
suggested.

Does this revised logic looks fine ?

if (log_buffer_state_local.buffer_full_cnt !=
		guc->log.prev_overflow_count[i]) {
	new_overflow = 1;
	guc->log.total_overflow_count[i] += 
(log_buffer_state_local.buffer_full_cnt - guc->log.prev_overflow_count[i]);

	if (log_buffer_state_local.buffer_full_cnt < 
guc->log.prev_overflow_count[i])
		guc->log.total_overflow_count[i] += 15;

	log_buffer_state_local.buffer_full_cnt = guc->log.prev_overflow_count[i];
}


> Regards,
>
> Tvrtko
>
>
>
>