On 13/05/16 15:36, Dave Gordon wrote:
Rather than wait to see whether more space becomes available in the GuC
submission workqueue, we can just return -EAGAIN and let the caller try
again in a little while. This gets rid of an uninterruptable sleep in
the polling code :)
We'll also add a counter to the GuC client statistics, to see how often
we find the WQ full.
v2:
Flag the likely() code path (Tvtrko Ursulin).
v4:
Add/update comments about failure counters (Tvtrko Ursulin).
Signed-off-by: Dave Gordon <david.s.gordon@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_debugfs.c | 1 +
drivers/gpu/drm/i915/i915_guc_submission.c | 18 +++++++-----------
drivers/gpu/drm/i915/intel_guc.h | 22 ++++++++++++++++------
3 files changed, 24 insertions(+), 17 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 24f4105..de05841 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2506,6 +2506,7 @@ static void i915_guc_client_info(struct seq_file *m,
seq_printf(m, "\tWQ size %d, offset: 0x%x, tail %d\n",
client->wq_size, client->wq_offset, client->wq_tail);
+ seq_printf(m, "\tWork queue full: %u\n", client->no_wq_space);
seq_printf(m, "\tFailed to queue: %u\n", client->q_fail);
seq_printf(m, "\tFailed doorbell: %u\n", client->b_fail);
seq_printf(m, "\tLast submission result: %d\n", client->retcode);
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
index 87cb739..85b2b89 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -468,26 +468,22 @@ static void guc_fini_ctx_desc(struct intel_guc *guc,
*/
int i915_guc_wq_check_space(struct drm_i915_gem_request *request)
{
- const size_t size = sizeof(struct guc_wq_item);
+ const size_t wqi_size = sizeof(struct guc_wq_item);
struct i915_guc_client *gc = request->i915->guc.execbuf_client;
struct guc_process_desc *desc;
- int ret = -ETIMEDOUT, timeout_counter = 200;
+ u32 freespace;
GEM_BUG_ON(gc == NULL);
desc = gc->client_base + gc->proc_desc_offset;
- while (timeout_counter-- > 0) {
- if (CIRC_SPACE(gc->wq_tail, desc->head, gc->wq_size) >= size) {
- ret = 0;
- break;
- }
+ freespace = CIRC_SPACE(gc->wq_tail, desc->head, gc->wq_size);
+ if (likely(freespace >= wqi_size))
+ return 0;
- if (timeout_counter)
- usleep_range(1000, 2000);
- };
+ gc->no_wq_space += 1;
- return ret;
+ return -EAGAIN;
}
static int guc_add_workqueue_item(struct i915_guc_client *gc,
diff --git a/drivers/gpu/drm/i915/intel_guc.h b/drivers/gpu/drm/i915/intel_guc.h
index 91f315c..380a743 100644
--- a/drivers/gpu/drm/i915/intel_guc.h
+++ b/drivers/gpu/drm/i915/intel_guc.h
@@ -48,9 +48,18 @@ struct drm_i915_gem_request;
* queue (a circular array of work items), again described in the process
* descriptor. Work queue pages are mapped momentarily as required.
*
- * Finally, we also keep a few statistics here, including the number of
- * submissions to each engine, and a record of the last submission failure
- * (if any).
+ * We also keep a few statistics on failures. Ideally, these should all
+ * be zero!
+ * no_wq_space: times that the submission pre-check found no space was
+ * available in the work queue (note, the queue is shared,
+ * not per-engine). It is OK for this to be nonzero, but
+ * it should not be huge!
+ * q_fail: failed to enqueue a work item. This should never happen,
+ * because we check for space beforehand.
+ * b_fail: failed to ring the doorbell. This should never happen, unless
+ * somehow the hardware misbehaves, or maybe if the GuC firmware
+ * crashes? We probably need to reset the GPU to recover.
+ * retcode: errno from last guc_submit()
*/
struct i915_guc_client {
struct drm_i915_gem_object *client_obj;
@@ -71,12 +80,13 @@ struct i915_guc_client {
uint32_t wq_tail;
uint32_t unused; /* Was 'wq_head' */
- /* GuC submission statistics & status */
- uint64_t submissions[GUC_MAX_ENGINES_NUM];
+ uint32_t no_wq_space;
uint32_t q_fail;
uint32_t b_fail;
int retcode;
- int spare; /* pad to 32 DWords */
+
+ /* Per-engine counts of GuC submissions */
+ uint64_t submissions[GUC_MAX_ENGINES_NUM];
};
enum intel_guc_fw_status {
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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