Re: [PATCH 2/3] drm/amdgpu: More efficient ring padding

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On 12/07/2024 16:28, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>

Having noticed that typically 200+ nops per submission are written into
the ring, using a rather verbose one-nop-at-a-time-plus-ring-buffer-
arithmetic as done in amdgpu_ring_write(), the obvious idea was to
improve it by filling those nops in blocks.

This patch therefore adds the amdgpu_ring_fill() helper which can do the
business in at most two memset32 calls.

The performance gains are not that amazing for normal workloads though.
For instance a game which results in two submissions per frame, each pads
with 222 nops, submission worker thread profile changes from:

+   90.78%     0.67%  kworker/u32:3-e  [kernel.kallsyms]  [k] process_one_work
+   48.92%     0.12%  kworker/u32:3-e  [kernel.kallsyms]  [k] commit_tail
+   41.18%     1.73%  kworker/u32:3-e  [kernel.kallsyms]  [k] amdgpu_dm_atomic_commit_tail
-   30.31%     0.67%  kworker/u32:3-e  [kernel.kallsyms]  [k] drm_sched_run_job_work
    - 29.63% drm_sched_run_job_work
       + 8.55% dma_fence_add_callback
       - 7.50% amdgpu_job_run
          - 7.43% amdgpu_ib_schedule
             - 2.46% amdgpu_ring_commit
                  1.44% amdgpu_ring_insert_nop

To:

+   88.28%     0.21%  kworker/u32:4-e  [kernel.kallsyms]  [k] process_one_work
+   45.22%     0.12%  kworker/u32:4-e  [kernel.kallsyms]  [k] commit_tail
+   37.93%     1.86%  kworker/u32:4-e  [kernel.kallsyms]  [k] amdgpu_dm_atomic_commit_tail
-   29.28%     1.11%  kworker/u32:4-e  [kernel.kallsyms]  [k] drm_sched_run_job_work
    - 28.16% drm_sched_run_job_work
       + 9.93% dma_fence_add_callback
       - 6.84% amdgpu_job_run
          - 6.27% amdgpu_ib_schedule
               1.23% gfx_v10_0_ring_emit_fence
               1.20% amdgpu_ring_commit

But if we run a more "spammy" workload, which does several orders of
magnitude more submissions second we go from:

+   79.38%     1.66%  kworker/u32:1+e  [kernel.kallsyms]  [k] process_one_work
-   63.13%     6.66%  kworker/u32:1+e  [kernel.kallsyms]  [k] drm_sched_run_job_work
    - 56.47% drm_sched_run_job_work
       - 25.67% amdgpu_job_run
          - 24.40% amdgpu_ib_schedule
             - 15.29% amdgpu_ring_commit
                  12.06% amdgpu_ring_insert_nop

To:

+   77.83%     2.07%  kworker/u32:2-e  [kernel.kallsyms]  [k] process_one_work
-   61.03%     7.75%  kworker/u32:2-e  [kernel.kallsyms]  [k] drm_sched_run_job_work
    - 53.27% drm_sched_run_job_work
       - 17.31% amdgpu_job_run
          - 16.34% amdgpu_ib_schedule
             - 7.17% amdgpu_ring_commit
                  1.67% amdgpu_ring_insert_nop

Which is a noticeable improvement in time spent by amdgpu_ring_commit
inserting nops.

v2:
  * Use a much more sensible "fill" approach.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
Cc: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c | 22 ++++++++++++++-----
  drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h | 27 ++++++++++++++++++++++++
  drivers/gpu/drm/amd/amdgpu/amdgpu_vpe.c  | 13 ++++++------
  drivers/gpu/drm/amd/amdgpu/cik_sdma.c    | 15 +++++++------
  drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c   | 16 ++++++++------
  drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c   | 16 ++++++++------
  drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c   | 16 ++++++++------
  drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c | 16 ++++++++------
  drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c   | 16 ++++++++------
  drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c   | 16 ++++++++------
  drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c   | 16 ++++++++------
  drivers/gpu/drm/amd/amdgpu/sdma_v7_0.c   | 16 ++++++++------
  12 files changed, 130 insertions(+), 75 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
index 1a1963318424..7fccd9ed9bdb 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
@@ -108,10 +108,17 @@ int amdgpu_ring_alloc(struct amdgpu_ring *ring, unsigned int ndw)
   */
  void amdgpu_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
-	int i;
+	if (count == 0)
+		return;
- for (i = 0; i < count; i++)
-		amdgpu_ring_write(ring, ring->funcs->nop);
+	if (count > 1) {
+		amdgpu_ring_fill(ring, ring->funcs->nop, count);
+	} else {
+		int i;
+
+		for (i = 0; i < count; i++)
+			amdgpu_ring_write(ring, ring->funcs->nop);
+	}
  }
/**
@@ -124,8 +131,13 @@ void amdgpu_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
   */
  void amdgpu_ring_generic_pad_ib(struct amdgpu_ring *ring, struct amdgpu_ib *ib)
  {
-	while (ib->length_dw & ring->funcs->align_mask)
-		ib->ptr[ib->length_dw++] = ring->funcs->nop;
+	u32 count = ib->length_dw & ring->funcs->align_mask;

This is wrong.. I'll re-spin next week.

Regards,

Tvrtko

+
+	if (count) {
+		memset32(&ib->ptr[ib->length_dw], ring->funcs->nop, count);
+
+		ib->length_dw += count;
+	}
  }
/**
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
index 582053f1cd56..2264d7502eb6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
@@ -412,6 +412,33 @@ static inline void amdgpu_ring_write_multiple(struct amdgpu_ring *ring,
  	ring->count_dw -= count_dw;
  }
+static inline void amdgpu_ring_fill(struct amdgpu_ring *ring, u32 v,
+				    unsigned int count_dw)
+{
+	unsigned int occupied, chunk1, chunk2;
+
+	if (!count_dw)
+		return;
+
+	if (unlikely(ring->count_dw < count_dw))
+		DRM_ERROR("amdgpu: writing more dwords to the ring than expected!\n");
+
+	occupied = ring->wptr & ring->buf_mask;
+	chunk1 = ring->buf_mask + 1 - occupied;
+	chunk1 = (chunk1 >= count_dw) ? count_dw : chunk1;
+	chunk2 = count_dw - chunk1;
+
+	if (chunk1)
+		memset32((u32 *)&ring->ring[occupied], v, chunk1);
+
+	if (chunk2)
+		memset32((u32 *)&ring->ring[0], v, chunk2);
+
+	ring->wptr += count_dw;
+	ring->wptr &= ring->ptr_mask;
+	ring->count_dw -= count_dw;
+}
+
  /**
   * amdgpu_ring_patch_cond_exec - patch dw count of conditional execute
   * @ring: amdgpu_ring structure
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vpe.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vpe.c
index 5acd20ff5979..61a9766b02e3 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vpe.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vpe.c
@@ -452,14 +452,13 @@ static int vpe_resume(void *handle)
static void vpe_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
-	int i;
+	u32 nop = ring->funcs->nop;
- for (i = 0; i < count; i++)
-		if (i == 0)
-			amdgpu_ring_write(ring, ring->funcs->nop |
-				VPE_CMD_NOP_HEADER_COUNT(count - 1));
-		else
-			amdgpu_ring_write(ring, ring->funcs->nop);
+	if (!count)
+		return;
+
+	amdgpu_ring_write(ring, nop | VPE_CMD_NOP_HEADER_COUNT(--count));
+	amdgpu_ring_fill(ring, nop, count);
  }
static uint64_t vpe_get_csa_mc_addr(struct amdgpu_ring *ring, uint32_t vmid)
diff --git a/drivers/gpu/drm/amd/amdgpu/cik_sdma.c b/drivers/gpu/drm/amd/amdgpu/cik_sdma.c
index 952737de9411..1b7742728bf0 100644
--- a/drivers/gpu/drm/amd/amdgpu/cik_sdma.c
+++ b/drivers/gpu/drm/amd/amdgpu/cik_sdma.c
@@ -198,14 +198,15 @@ static void cik_sdma_ring_set_wptr(struct amdgpu_ring *ring)
  static void cik_sdma_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
  	struct amdgpu_sdma_instance *sdma = amdgpu_sdma_get_instance_from_ring(ring);
-	int i;
+	u32 nop = ring->funcs->nop;
- for (i = 0; i < count; i++)
-		if (sdma && sdma->burst_nop && (i == 0))
-			amdgpu_ring_write(ring, ring->funcs->nop |
-					  SDMA_NOP_COUNT(count - 1));
-		else
-			amdgpu_ring_write(ring, ring->funcs->nop);
+	if (!count)
+		return;
+
+	if (sdma && sdma->burst_nop)
+		amdgpu_ring_write(ring, nop | SDMA_NOP_COUNT(--count));
+
+	amdgpu_ring_fill(ring, nop, count);
  }
/**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c b/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c
index 725392522267..4061f7a4d055 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c
@@ -222,14 +222,16 @@ static void sdma_v2_4_ring_set_wptr(struct amdgpu_ring *ring)
  static void sdma_v2_4_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
  	struct amdgpu_sdma_instance *sdma = amdgpu_sdma_get_instance_from_ring(ring);
-	int i;
+	u32 nop = ring->funcs->nop;
- for (i = 0; i < count; i++)
-		if (sdma && sdma->burst_nop && (i == 0))
-			amdgpu_ring_write(ring, ring->funcs->nop |
-				SDMA_PKT_NOP_HEADER_COUNT(count - 1));
-		else
-			amdgpu_ring_write(ring, ring->funcs->nop);
+	if (!count)
+		return;
+
+	if (sdma && sdma->burst_nop)
+		amdgpu_ring_write(ring,
+				  nop | SDMA_PKT_NOP_HEADER_COUNT(--count));
+
+	amdgpu_ring_fill(ring, nop, count);
  }
/**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
index aa637541da58..f655b5c32bd8 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
@@ -398,14 +398,16 @@ static void sdma_v3_0_ring_set_wptr(struct amdgpu_ring *ring)
  static void sdma_v3_0_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
  	struct amdgpu_sdma_instance *sdma = amdgpu_sdma_get_instance_from_ring(ring);
-	int i;
+	u32 nop = ring->funcs->nop;
- for (i = 0; i < count; i++)
-		if (sdma && sdma->burst_nop && (i == 0))
-			amdgpu_ring_write(ring, ring->funcs->nop |
-				SDMA_PKT_NOP_HEADER_COUNT(count - 1));
-		else
-			amdgpu_ring_write(ring, ring->funcs->nop);
+	if (!count)
+		return;
+
+	if (sdma && sdma->burst_nop)
+		amdgpu_ring_write(ring,
+				  nop | SDMA_PKT_NOP_HEADER_COUNT(--count));
+
+	amdgpu_ring_fill(ring, nop, count);
  }
/**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
index 772604feb6ac..bc8bb6b184af 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
@@ -737,14 +737,16 @@ static void sdma_v4_0_page_ring_set_wptr(struct amdgpu_ring *ring)
  static void sdma_v4_0_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
  	struct amdgpu_sdma_instance *sdma = amdgpu_sdma_get_instance_from_ring(ring);
-	int i;
+	u32 nop = ring->funcs->nop;
- for (i = 0; i < count; i++)
-		if (sdma && sdma->burst_nop && (i == 0))
-			amdgpu_ring_write(ring, ring->funcs->nop |
-				SDMA_PKT_NOP_HEADER_COUNT(count - 1));
-		else
-			amdgpu_ring_write(ring, ring->funcs->nop);
+	if (!count)
+		return;
+
+	if (sdma && sdma->burst_nop)
+		amdgpu_ring_write(ring,
+				  nop | SDMA_PKT_NOP_HEADER_COUNT(--count));
+
+	amdgpu_ring_fill(ring, nop, count);
  }
/**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c b/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c
index 01644a869738..3425cf35c0d6 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c
@@ -290,14 +290,16 @@ static void sdma_v4_4_2_page_ring_set_wptr(struct amdgpu_ring *ring)
  static void sdma_v4_4_2_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
  	struct amdgpu_sdma_instance *sdma = amdgpu_sdma_get_instance_from_ring(ring);
-	int i;
+	u32 nop = ring->funcs->nop;
- for (i = 0; i < count; i++)
-		if (sdma && sdma->burst_nop && (i == 0))
-			amdgpu_ring_write(ring, ring->funcs->nop |
-				SDMA_PKT_NOP_HEADER_COUNT(count - 1));
-		else
-			amdgpu_ring_write(ring, ring->funcs->nop);
+	if (!count)
+		return;
+
+	if (sdma && sdma->burst_nop)
+		amdgpu_ring_write(ring,
+				  nop | SDMA_PKT_NOP_HEADER_COUNT(--count));
+
+	amdgpu_ring_fill(ring, nop, count);
  }
/**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
index b7d33d78bce0..fa6591e9769a 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
@@ -387,14 +387,16 @@ static void sdma_v5_0_ring_set_wptr(struct amdgpu_ring *ring)
  static void sdma_v5_0_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
  	struct amdgpu_sdma_instance *sdma = amdgpu_sdma_get_instance_from_ring(ring);
-	int i;
+	u32 nop = ring->funcs->nop;
- for (i = 0; i < count; i++)
-		if (sdma && sdma->burst_nop && (i == 0))
-			amdgpu_ring_write(ring, ring->funcs->nop |
-				SDMA_PKT_NOP_HEADER_COUNT(count - 1));
-		else
-			amdgpu_ring_write(ring, ring->funcs->nop);
+	if (!count)
+		return;
+
+	if (sdma && sdma->burst_nop)
+		amdgpu_ring_write(ring,
+				  nop | SDMA_PKT_NOP_HEADER_COUNT(--count));
+
+	amdgpu_ring_fill(ring, nop, count);
  }
/**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c b/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
index cc9e961f0078..f95e2831447e 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
@@ -194,14 +194,16 @@ static void sdma_v5_2_ring_set_wptr(struct amdgpu_ring *ring)
  static void sdma_v5_2_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
  	struct amdgpu_sdma_instance *sdma = amdgpu_sdma_get_instance_from_ring(ring);
-	int i;
+	u32 nop = ring->funcs->nop;
- for (i = 0; i < count; i++)
-		if (sdma && sdma->burst_nop && (i == 0))
-			amdgpu_ring_write(ring, ring->funcs->nop |
-				SDMA_PKT_NOP_HEADER_COUNT(count - 1));
-		else
-			amdgpu_ring_write(ring, ring->funcs->nop);
+	if (!count)
+		return;
+
+	if (sdma && sdma->burst_nop)
+		amdgpu_ring_write(ring,
+				  nop | SDMA_PKT_NOP_HEADER_COUNT(--count));
+
+	amdgpu_ring_fill(ring, nop, count);
  }
/**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c
index dab4c2db8c9d..aabe4dc37876 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c
@@ -181,14 +181,16 @@ static void sdma_v6_0_ring_set_wptr(struct amdgpu_ring *ring)
  static void sdma_v6_0_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
  	struct amdgpu_sdma_instance *sdma = amdgpu_sdma_get_instance_from_ring(ring);
-	int i;
+	u32 nop = ring->funcs->nop;
- for (i = 0; i < count; i++)
-		if (sdma && sdma->burst_nop && (i == 0))
-			amdgpu_ring_write(ring, ring->funcs->nop |
-				SDMA_PKT_NOP_HEADER_COUNT(count - 1));
-		else
-			amdgpu_ring_write(ring, ring->funcs->nop);
+	if (!count)
+		return;
+
+	if (sdma && sdma->burst_nop)
+		amdgpu_ring_write(ring,
+				  nop | SDMA_PKT_NOP_HEADER_COUNT(--count));
+
+	amdgpu_ring_fill(ring, nop, count);
  }
/*
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v7_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v7_0.c
index 96514fd77e35..37ca21dc9678 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v7_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v7_0.c
@@ -206,14 +206,16 @@ static void sdma_v7_0_ring_set_wptr(struct amdgpu_ring *ring)
  static void sdma_v7_0_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
  	struct amdgpu_sdma_instance *sdma = amdgpu_sdma_get_instance_from_ring(ring);
-	int i;
+	u32 nop = ring->funcs->nop;
- for (i = 0; i < count; i++)
-		if (sdma && sdma->burst_nop && (i == 0))
-			amdgpu_ring_write(ring, ring->funcs->nop |
-				SDMA_PKT_NOP_HEADER_COUNT(count - 1));
-		else
-			amdgpu_ring_write(ring, ring->funcs->nop);
+	if (!count)
+		return;
+
+	if (sdma && sdma->burst_nop)
+		amdgpu_ring_write(ring,
+				  nop | SDMA_PKT_NOP_HEADER_COUNT(--count));
+
+	amdgpu_ring_fill(ring, nop, count);
  }
/**



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