drm/i915/perf: rate limit spurious oa report notice

This change is pre-emptively aiming to avoid a potential cause of kernel
logging noise in case some condition were to result in us seeing invalid
OA reports.

The workaround for the OA unit's tail pointer race condition is what
avoids the primary known cause of invalid reports being seen and with
that in place we aren't expecting to see this notice but it can't be
entirely ruled out.

Just in case some condition does lead to the notice then it's likely
that it will be triggered repeatedly while attempting to append a
sequence of reports and depending on the configured OA sampling
frequency that might be a large number of repeat notices.

v2: (Chris) avoid inconsistent warning on throttle with
    printk_ratelimit()
v3: (Matt) init and summarise with stream init/close not driver init/fini

Signed-off-by: Robert Bragg <robert@sixbynine.org>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170511154345.962-9-lionel.g.landwerlin@intel.com
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 22b2ea3ea66f7b68baf986f3385400dd94420188..66dee15e4fc01c61467b73f0bcb713caf81f0df8 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2354,6 +2354,12 @@ struct drm_i915_private {
                        wait_queue_head_t poll_wq;
                        bool pollin;
 
+                       /**
+                        * For rate limiting any notifications of spurious
+                        * invalid OA reports
+                        */
+                       struct ratelimit_state spurious_report_rs;
+
                        bool periodic;
                        int period_exponent;
 

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 4d31b70df4529245bf5d88078fdd72341c0f245a..85269bcc8372c623021d278942e1cc3461cbeb95 100644 (file)
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -632,7 +632,8 @@ static int gen7_append_oa_reports(struct i915_perf_stream *stream,
                 * copying it to userspace...
                 */
                if (report32[0] == 0) {
-                       DRM_NOTE("Skipping spurious, invalid OA report\n");
+                       if (__ratelimit(&dev_priv->perf.oa.spurious_report_rs))
+                               DRM_NOTE("Skipping spurious, invalid OA report\n");
                        continue;
                }
 
@@ -911,6 +912,11 @@ static void i915_oa_stream_destroy(struct i915_perf_stream *stream)
                oa_put_render_ctx_id(stream);
 
        dev_priv->perf.oa.exclusive_stream = NULL;
+
+       if (dev_priv->perf.oa.spurious_report_rs.missed) {
+               DRM_NOTE("%d spurious OA report notices suppressed due to ratelimiting\n",
+                        dev_priv->perf.oa.spurious_report_rs.missed);
+       }
 }
 
 static void gen7_init_oa_buffer(struct drm_i915_private *dev_priv)
@@ -1266,6 +1272,26 @@ static int i915_oa_stream_init(struct i915_perf_stream *stream,
                return -EINVAL;
        }
 
+       /* We set up some ratelimit state to potentially throttle any _NOTES
+        * about spurious, invalid OA reports which we don't forward to
+        * userspace.
+        *
+        * The initialization is associated with opening the stream (not driver
+        * init) considering we print a _NOTE about any throttling when closing
+        * the stream instead of waiting until driver _fini which no one would
+        * ever see.
+        *
+        * Using the same limiting factors as printk_ratelimit()
+        */
+       ratelimit_state_init(&dev_priv->perf.oa.spurious_report_rs,
+                            5 * HZ, 10);
+       /* Since we use a DRM_NOTE for spurious reports it would be
+        * inconsistent to let __ratelimit() automatically print a warning for
+        * throttling.
+        */
+       ratelimit_set_flags(&dev_priv->perf.oa.spurious_report_rs,
+                           RATELIMIT_MSG_ON_RELEASE);
+
        stream->sample_size = sizeof(struct drm_i915_perf_record_header);
 
        format_size = dev_priv->perf.oa.oa_formats[props->oa_format].size;