From: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
Assorted changes in the areas of code cleanup, reduction of
invariant conditional in the interrupt handler and lock
contention and MMIO access optimisation.
* Remove needless initialization.
* Improve cache locality by reorganizing code and/or using
branch hints to keep unexpected or error conditions out
of line.
* Favor busy submit path vs. empty queue.
* Less branching in hot-paths.
v2:
* Avoid mmio reads when possible. (Chris Wilson)
* Use natural integer size for csb indices.
* Remove useless return value from execlists_update_context.
* Extract 32-bit ppgtt PDPs update so it is out of line and
shared with two callers.
* Grab forcewake across all mmio operations to ease the
load on uncore lock and use chepear mmio ops.
v3:
* Removed some more pointless u8 data types.
* Removed unused return from execlists_context_queue.
* Commit message updates.
v4:
* Unclumsify the unqueue if statement. (Chris Wilson)
* Hide forcewake from the queuing function. (Chris Wilson)
Version 3 now makes the irq handling code path ~20% smaller on
48-bit PPGTT hardware, and a little bit less elsewhere. Hot
paths are mostly in-line now and hammering on the uncore
spinlock is greatly reduced together with mmio traffic to an
extent.
Benchmarking with "gem_latency -n 100" (keep submitting
batches with 100 nop instruction) shows approximately 4% higher
throughput, 2% less CPU time and 22% smaller latencies. This was
on a big-core while small-cores could benefit even more.
Most likely reason for the improvements are the MMIO
optimization and uncore lock traffic reduction.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
Cc: Chris Wilson <ch...@chris-wilson.co.uk>
---
drivers/gpu/drm/i915/intel_lrc.c | 214 +++++++++++++++++---------------
drivers/gpu/drm/i915/intel_ringbuffer.h | 3 +-
2 files changed, 114 insertions(+), 103 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index f0a57afc8dff..247daf80664b 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -269,6 +269,9 @@ logical_ring_init_platform_invariants(struct
intel_engine_cs *ring)
{
struct drm_device *dev = ring->dev;
+ if (IS_GEN8(dev) || IS_GEN9(dev))
+ ring->idle_lite_restore_wa = ~0;
+
ring->disable_lite_restore_wa = (IS_SKL_REVID(dev, 0, SKL_REVID_B0) ||
IS_BXT_REVID(dev, 0, BXT_REVID_A1)) &&
(ring->id == VCS || ring->id == VCS2);
@@ -372,8 +375,6 @@ static void execlists_elsp_write(struct
drm_i915_gem_request *rq0,
rq0->elsp_submitted++;
/* You must always write both descriptors in the order below. */
- spin_lock(&dev_priv->uncore.lock);
- intel_uncore_forcewake_get__locked(dev_priv, FORCEWAKE_ALL);
I915_WRITE_FW(RING_ELSP(ring), upper_32_bits(desc[1]));
I915_WRITE_FW(RING_ELSP(ring), lower_32_bits(desc[1]));
@@ -383,11 +384,18 @@ static void execlists_elsp_write(struct
drm_i915_gem_request *rq0,
/* ELSP is a wo register, use another nearby reg for posting */
POSTING_READ_FW(RING_EXECLIST_STATUS_LO(ring));
- intel_uncore_forcewake_put__locked(dev_priv, FORCEWAKE_ALL);
- spin_unlock(&dev_priv->uncore.lock);
}
-static int execlists_update_context(struct drm_i915_gem_request *rq)
+static void
+execlists_update_context_pdps(struct i915_hw_ppgtt *ppgtt, u32 *reg_state)
+{
+ ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
+ ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
+ ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
+ ASSIGN_CTX_PDP(ppgtt, reg_state, 0);
+}
+
+static void execlists_update_context(struct drm_i915_gem_request *rq)
{
struct intel_engine_cs *ring = rq->ring;
struct i915_hw_ppgtt *ppgtt = rq->ctx->ppgtt;
@@ -395,19 +403,13 @@ static int execlists_update_context(struct
drm_i915_gem_request *rq)
reg_state[CTX_RING_TAIL+1] = rq->tail;
- if (ppgtt && !USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
- /* True 32b PPGTT with dynamic page allocation: update PDP
- * registers and point the unallocated PDPs to scratch page.
- * PML4 is allocated during ppgtt init, so this is not needed
- * in 48-bit mode.
- */
- ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
- ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
- ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
- ASSIGN_CTX_PDP(ppgtt, reg_state, 0);
- }
-
- return 0;
+ /* True 32b PPGTT with dynamic page allocation: update PDP
+ * registers and point the unallocated PDPs to scratch page.
+ * PML4 is allocated during ppgtt init, so this is not needed
+ * in 48-bit mode.
+ */
+ if (ppgtt && !USES_FULL_48BIT_PPGTT(ppgtt->base.dev))
+ execlists_update_context_pdps(ppgtt, reg_state);
}
static void execlists_submit_requests(struct drm_i915_gem_request *rq0,
@@ -421,10 +423,10 @@ static void execlists_submit_requests(struct
drm_i915_gem_request *rq0,
execlists_elsp_write(rq0, rq1);
}
-static void execlists_context_unqueue(struct intel_engine_cs *ring)
+static void execlists_context_unqueue__locked(struct intel_engine_cs *ring)
{
struct drm_i915_gem_request *req0 = NULL, *req1 = NULL;
- struct drm_i915_gem_request *cursor = NULL, *tmp = NULL;
+ struct drm_i915_gem_request *cursor, *tmp;
assert_spin_locked(&ring->execlist_lock);
@@ -434,9 +436,6 @@ static void execlists_context_unqueue(struct
intel_engine_cs *ring)
*/
WARN_ON(!intel_irqs_enabled(ring->dev->dev_private));
- if (list_empty(&ring->execlist_queue))
- return;
-
/* Try to read in pairs */
list_for_each_entry_safe(cursor, tmp, &ring->execlist_queue,
execlist_link) {
@@ -451,37 +450,48 @@ static void execlists_context_unqueue(struct
intel_engine_cs *ring)
req0 = cursor;
} else {
req1 = cursor;
+ WARN_ON(req1->elsp_submitted);
break;
}
}
- if (IS_GEN8(ring->dev) || IS_GEN9(ring->dev)) {
+ if (unlikely(!req0))
+ return;
+
+ if (req0->elsp_submitted & ring->idle_lite_restore_wa) {
/*
- * WaIdleLiteRestore: make sure we never cause a lite
- * restore with HEAD==TAIL
+ * WaIdleLiteRestore: make sure we never cause a lite restore
+ * with HEAD==TAIL.
+ *
+ * Apply the wa NOOPS to prevent ring:HEAD == req:TAIL as we
+ * resubmit the request. See gen8_emit_request() for where we
+ * prepare the padding after the end of the request.
*/
- if (req0->elsp_submitted) {
- /*
- * Apply the wa NOOPS to prevent ring:HEAD == req:TAIL
- * as we resubmit the request. See gen8_emit_request()
- * for where we prepare the padding after the end of the
- * request.
- */
- struct intel_ringbuffer *ringbuf;
+ struct intel_ringbuffer *ringbuf;
- ringbuf = req0->ctx->engine[ring->id].ringbuf;
- req0->tail += 8;
- req0->tail &= ringbuf->size - 1;
- }
+ ringbuf = req0->ctx->engine[ring->id].ringbuf;
+ req0->tail += 8;
+ req0->tail &= ringbuf->size - 1;
}
- WARN_ON(req1 && req1->elsp_submitted);
-
execlists_submit_requests(req0, req1);
}
-static bool execlists_check_remove_request(struct intel_engine_cs *ring,
- u32 request_id)
+static void execlists_context_unqueue(struct intel_engine_cs *ring)
+{
+ struct drm_i915_private *dev_priv = ring->dev->dev_private;
+
+ spin_lock(&dev_priv->uncore.lock);
+ intel_uncore_forcewake_get__locked(dev_priv, FORCEWAKE_ALL);
+
+ execlists_context_unqueue__locked(ring);
+
+ intel_uncore_forcewake_put__locked(dev_priv, FORCEWAKE_ALL);
+ spin_unlock(&dev_priv->uncore.lock);
+}
+
+static unsigned int
+execlists_check_remove_request(struct intel_engine_cs *ring, u32 request_id)
{
struct drm_i915_gem_request *head_req;
@@ -491,33 +501,41 @@ static bool execlists_check_remove_request(struct
intel_engine_cs *ring,
struct drm_i915_gem_request,
execlist_link);
- if (head_req != NULL) {
- if (intel_execlists_ctx_id(head_req->ctx, ring) == request_id) {
- WARN(head_req->elsp_submitted == 0,
- "Never submitted head request\n");
+ if (!head_req)
+ return 0;
- if (--head_req->elsp_submitted <= 0) {
- list_move_tail(&head_req->execlist_link,
-
&ring->execlist_retired_req_list);
- return true;
- }
- }
- }
+ if (unlikely(intel_execlists_ctx_id(head_req->ctx, ring) != request_id))
+ return 0;
+
+ WARN(head_req->elsp_submitted == 0, "Never submitted head request\n");
+
+ if (--head_req->elsp_submitted > 0)
+ return 0;
+
+ list_move_tail(&head_req->execlist_link,
+ &ring->execlist_retired_req_list);
- return false;
+ return 1;
}
-static void get_context_status(struct intel_engine_cs *ring,
- u8 read_pointer,
- u32 *status, u32 *context_id)
+static u32
+get_context_status(struct intel_engine_cs *ring, unsigned int read_pointer,
+ u32 *context_id)
{
struct drm_i915_private *dev_priv = ring->dev->dev_private;
+ u32 status;
- if (WARN_ON(read_pointer >= GEN8_CSB_ENTRIES))
- return;
+ read_pointer %= GEN8_CSB_ENTRIES;
+
+ status = I915_READ_FW(RING_CONTEXT_STATUS_BUF_LO(ring, read_pointer));
+
+ if (status & GEN8_CTX_STATUS_IDLE_ACTIVE)
+ return 0;
- *status = I915_READ(RING_CONTEXT_STATUS_BUF_LO(ring, read_pointer));
- *context_id = I915_READ(RING_CONTEXT_STATUS_BUF_HI(ring, read_pointer));
+ *context_id = I915_READ_FW(RING_CONTEXT_STATUS_BUF_HI(ring,
+ read_pointer));
+
+ return status;
}
/**
@@ -531,30 +549,27 @@ void intel_lrc_irq_handler(struct intel_engine_cs *ring)
{
struct drm_i915_private *dev_priv = ring->dev->dev_private;
u32 status_pointer;
- u8 read_pointer;
- u8 write_pointer;
+ unsigned int read_pointer, write_pointer;
u32 status = 0;
u32 status_id;
- u32 submit_contexts = 0;
+ unsigned int submit_contexts = 0;
+
+ spin_lock(&ring->execlist_lock);
- status_pointer = I915_READ(RING_CONTEXT_STATUS_PTR(ring));
+ spin_lock(&dev_priv->uncore.lock);
+ intel_uncore_forcewake_get__locked(dev_priv, FORCEWAKE_ALL);
+
+ status_pointer = I915_READ_FW(RING_CONTEXT_STATUS_PTR(ring));
read_pointer = ring->next_context_status_buffer;
write_pointer = GEN8_CSB_WRITE_PTR(status_pointer);
if (read_pointer > write_pointer)
write_pointer += GEN8_CSB_ENTRIES;
- spin_lock(&ring->execlist_lock);
-
while (read_pointer < write_pointer) {
+ status = get_context_status(ring, ++read_pointer, &status_id);
- get_context_status(ring, ++read_pointer % GEN8_CSB_ENTRIES,
- &status, &status_id);
-
- if (status & GEN8_CTX_STATUS_IDLE_ACTIVE)
- continue;
-
- if (status & GEN8_CTX_STATUS_PREEMPTED) {
+ if (unlikely(status & GEN8_CTX_STATUS_PREEMPTED)) {
if (status & GEN8_CTX_STATUS_LITE_RESTORE) {
if (execlists_check_remove_request(ring,
status_id))
WARN(1, "Lite Restored request removed
from queue\n");
@@ -562,37 +577,36 @@ void intel_lrc_irq_handler(struct intel_engine_cs *ring)
WARN(1, "Preemption without Lite Restore\n");
}
- if ((status & GEN8_CTX_STATUS_ACTIVE_IDLE) ||
- (status & GEN8_CTX_STATUS_ELEMENT_SWITCH)) {
- if (execlists_check_remove_request(ring, status_id))
- submit_contexts++;
- }
+ if (status & (GEN8_CTX_STATUS_ACTIVE_IDLE |
+ GEN8_CTX_STATUS_ELEMENT_SWITCH))
+ submit_contexts +=
+ execlists_check_remove_request(ring, status_id);
}
- if (ring->disable_lite_restore_wa) {
- /* Prevent a ctx to preempt itself */
- if ((status & GEN8_CTX_STATUS_ACTIVE_IDLE) &&
- (submit_contexts != 0))
- execlists_context_unqueue(ring);
- } else if (submit_contexts != 0) {
- execlists_context_unqueue(ring);
+ if (submit_contexts) {
+ if (!ring->disable_lite_restore_wa ||
+ (status & GEN8_CTX_STATUS_ACTIVE_IDLE))
+ execlists_context_unqueue__locked(ring);
}
- spin_unlock(&ring->execlist_lock);
-
- if (unlikely(submit_contexts > 2))
- DRM_ERROR("More than two context complete events?\n");
-
ring->next_context_status_buffer = write_pointer % GEN8_CSB_ENTRIES;
/* Update the read pointer to the old write pointer. Manual ringbuffer
* management ftw </sarcasm> */
- I915_WRITE(RING_CONTEXT_STATUS_PTR(ring),
- _MASKED_FIELD(GEN8_CSB_READ_PTR_MASK,
- ring->next_context_status_buffer << 8));
+ I915_WRITE_FW(RING_CONTEXT_STATUS_PTR(ring),
+ _MASKED_FIELD(GEN8_CSB_READ_PTR_MASK,
+ ring->next_context_status_buffer << 8));
+
+ intel_uncore_forcewake_put__locked(dev_priv, FORCEWAKE_ALL);
+ spin_unlock(&dev_priv->uncore.lock);
+
+ spin_unlock(&ring->execlist_lock);
+
+ if (unlikely(submit_contexts > 2))
+ DRM_ERROR("More than two context complete events?\n");
}
-static int execlists_context_queue(struct drm_i915_gem_request *request)
+static void execlists_context_queue(struct drm_i915_gem_request *request)
{
struct intel_engine_cs *ring = request->ring;
struct drm_i915_gem_request *cursor;
@@ -629,8 +643,6 @@ static int execlists_context_queue(struct
drm_i915_gem_request *request)
execlists_context_unqueue(ring);
spin_unlock_irq(&ring->execlist_lock);
-
- return 0;
}
static int logical_ring_invalidate_all_caches(struct drm_i915_gem_request *req)
@@ -1549,7 +1561,7 @@ static int gen8_init_common_ring(struct intel_engine_cs
*ring)
{
struct drm_device *dev = ring->dev;
struct drm_i915_private *dev_priv = dev->dev_private;
- u8 next_context_status_buffer_hw;
+ unsigned int next_context_status_buffer_hw;
lrc_setup_hardware_status_page(ring,
dev_priv->kernel_context->engine[ring->id].state);
@@ -2012,6 +2024,7 @@ void intel_logical_ring_cleanup(struct intel_engine_cs
*ring)
ring->status_page.obj = NULL;
}
+ ring->idle_lite_restore_wa = 0;
ring->disable_lite_restore_wa = false;
ring->ctx_desc_template = 0;
@@ -2416,10 +2429,7 @@ populate_lr_context(struct intel_context *ctx, struct
drm_i915_gem_object *ctx_o
* With dynamic page allocation, PDPs may not be allocated at
* this point. Point the unallocated PDPs to the scratch page
*/
- ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
- ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
- ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
- ASSIGN_CTX_PDP(ppgtt, reg_state, 0);
+ execlists_update_context_pdps(ppgtt, reg_state);
}
if (ring->id == RCS) {
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h
b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 566b0ae10ce0..dd910d30a380 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -271,7 +271,8 @@ struct intel_engine_cs {
spinlock_t execlist_lock;
struct list_head execlist_queue;
struct list_head execlist_retired_req_list;
- u8 next_context_status_buffer;
+ unsigned int next_context_status_buffer;
+ unsigned int idle_lite_restore_wa;
bool disable_lite_restore_wa;
u32 ctx_desc_template;
u32 irq_keep_mask; /* bitmask for interrupts that should
not be masked */
--
1.9.1
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