[PATCH 2/2] drm/amdgpu: workaround to avoid SET_Q_MODE packets
Alex Deucher
alexdeucher at gmail.com
Thu Feb 29 15:38:35 UTC 2024
On Thu, Feb 29, 2024 at 9:58 AM Christian König
<ckoenig.leichtzumerken at gmail.com> wrote:
>
> It turned out that executing the SET_Q_MODE packet on every submission
> creates to much overhead.
>
> Implement a workaround which allows skipping the SET_Q_MODE packet if
> subsequent submissions all use the same parameters.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
Series is:
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h | 3 +
> drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c | 104 +++++++++++++++++++----
> 2 files changed, 92 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> index 756330767909..582053f1cd56 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> @@ -285,6 +285,9 @@ struct amdgpu_ring {
> unsigned cond_exe_offs;
> u64 cond_exe_gpu_addr;
> volatile u32 *cond_exe_cpu_addr;
> + unsigned int set_q_mode_offs;
> + volatile u32 *set_q_mode_ptr;
> + u64 set_q_mode_token;
> unsigned vm_hub;
> unsigned vm_inv_eng;
> struct dma_fence *vmid_wait;
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c
> index 2ccbdee570cf..6e6b6eff48e2 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c
> @@ -5461,6 +5461,11 @@ static void gfx_v11_0_ring_emit_vm_flush(struct amdgpu_ring *ring,
> amdgpu_ring_write(ring, PACKET3(PACKET3_PFP_SYNC_ME, 0));
> amdgpu_ring_write(ring, 0x0);
> }
> +
> + /* Make sure that we can't skip the SET_Q_MODE packets when the VM
> + * changed in any way.
> + */
> + ring->set_q_mode_ptr = NULL;
> }
>
> static void gfx_v11_0_ring_emit_fence_kiq(struct amdgpu_ring *ring, u64 addr,
> @@ -5510,16 +5515,81 @@ static void gfx_v11_0_ring_emit_cntxcntl(struct amdgpu_ring *ring,
> amdgpu_ring_write(ring, 0);
> }
>
> +static unsigned gfx_v11_0_ring_emit_init_cond_exec(struct amdgpu_ring *ring,
> + uint64_t addr)
> +{
> + unsigned ret;
> +
> + amdgpu_ring_write(ring, PACKET3(PACKET3_COND_EXEC, 3));
> + amdgpu_ring_write(ring, lower_32_bits(addr));
> + amdgpu_ring_write(ring, upper_32_bits(addr));
> + /* discard following DWs if *cond_exec_gpu_addr==0 */
> + amdgpu_ring_write(ring, 0);
> + ret = ring->wptr & ring->buf_mask;
> + /* patch dummy value later */
> + amdgpu_ring_write(ring, 0);
> +
> + return ret;
> +}
> +
> static void gfx_v11_0_ring_emit_gfx_shadow(struct amdgpu_ring *ring,
> u64 shadow_va, u64 csa_va,
> u64 gds_va, bool init_shadow,
> int vmid)
> {
> struct amdgpu_device *adev = ring->adev;
> + unsigned int offs, end;
>
> if (!adev->gfx.cp_gfx_shadow)
> return;
>
> + /*
> + * The logic here isn't easy to understand because we need to keep state
> + * accross multiple executions of the function as well as between the
> + * CPU and GPU. The general idea is that the newly written GPU command
> + * has a condition on the previous one and only executed if really
> + * necessary.
> + */
> +
> + /*
> + * The dw in the NOP controls if the next SET_Q_MODE packet should be
> + * executed or not. Reserve 64bits just to be on the save side.
> + */
> + amdgpu_ring_write(ring, PACKET3(PACKET3_NOP, 1));
> + offs = ring->wptr & ring->buf_mask;
> +
> + /*
> + * We start with skipping the prefix SET_Q_MODE and always executing
> + * the postfix SET_Q_MODE packet. This is changed below with a
> + * WRITE_DATA command when the postfix executed.
> + */
> + amdgpu_ring_write(ring, shadow_va ? 1 : 0);
> + amdgpu_ring_write(ring, 0);
> +
> + if (ring->set_q_mode_offs) {
> + uint64_t addr;
> +
> + addr = amdgpu_bo_gpu_offset(ring->ring_obj);
> + addr += ring->set_q_mode_offs << 2;
> + end = gfx_v11_0_ring_emit_init_cond_exec(ring, addr);
> + }
> +
> + /*
> + * When the postfix SET_Q_MODE packet executes we need to make sure that the
> + * next prefix SET_Q_MODE packet executes as well.
> + */
> + if (!shadow_va) {
> + uint64_t addr;
> +
> + addr = amdgpu_bo_gpu_offset(ring->ring_obj);
> + addr += offs << 2;
> + amdgpu_ring_write(ring, PACKET3(PACKET3_WRITE_DATA, 3));
> + amdgpu_ring_write(ring, WRITE_DATA_DST_SEL(5) | WR_CONFIRM);
> + amdgpu_ring_write(ring, lower_32_bits(addr));
> + amdgpu_ring_write(ring, upper_32_bits(addr));
> + amdgpu_ring_write(ring, 0x1);
> + }
> +
> amdgpu_ring_write(ring, PACKET3(PACKET3_SET_Q_PREEMPTION_MODE, 7));
> amdgpu_ring_write(ring, lower_32_bits(shadow_va));
> amdgpu_ring_write(ring, upper_32_bits(shadow_va));
> @@ -5531,23 +5601,26 @@ static void gfx_v11_0_ring_emit_gfx_shadow(struct amdgpu_ring *ring,
> PACKET3_SET_Q_PREEMPTION_MODE_IB_VMID(vmid) : 0);
> amdgpu_ring_write(ring, init_shadow ?
> PACKET3_SET_Q_PREEMPTION_MODE_INIT_SHADOW_MEM : 0);
> -}
>
> -static unsigned gfx_v11_0_ring_emit_init_cond_exec(struct amdgpu_ring *ring,
> - uint64_t addr)
> -{
> - unsigned ret;
> + if (ring->set_q_mode_offs)
> + amdgpu_ring_patch_cond_exec(ring, end);
>
> - amdgpu_ring_write(ring, PACKET3(PACKET3_COND_EXEC, 3));
> - amdgpu_ring_write(ring, lower_32_bits(addr));
> - amdgpu_ring_write(ring, upper_32_bits(addr));
> - /* discard following DWs if *cond_exec_gpu_addr==0 */
> - amdgpu_ring_write(ring, 0);
> - ret = ring->wptr & ring->buf_mask;
> - /* patch dummy value later */
> - amdgpu_ring_write(ring, 0);
> + if (shadow_va) {
> + uint64_t token = shadow_va ^ csa_va ^ gds_va ^ vmid;
>
> - return ret;
> + /*
> + * If the tokens match try to skip the last postfix SET_Q_MODE
> + * packet to avoid saving/restoring the state all the time.
> + */
> + if (ring->set_q_mode_ptr && ring->set_q_mode_token == token)
> + *ring->set_q_mode_ptr = 0;
> +
> + ring->set_q_mode_token = token;
> + } else {
> + ring->set_q_mode_ptr = &ring->ring[ring->set_q_mode_offs];
> + }
> +
> + ring->set_q_mode_offs = offs;
> }
>
> static int gfx_v11_0_ring_preempt_ib(struct amdgpu_ring *ring)
> @@ -6114,7 +6187,7 @@ static const struct amdgpu_ring_funcs gfx_v11_0_ring_funcs_gfx = {
> .emit_frame_size = /* totally 247 maximum if 16 IBs */
> 5 + /* update_spm_vmid */
> 5 + /* COND_EXEC */
> - 9 + /* SET_Q_PREEMPTION_MODE */
> + 22 + /* SET_Q_PREEMPTION_MODE */
> 7 + /* PIPELINE_SYNC */
> SOC15_FLUSH_GPU_TLB_NUM_WREG * 5 +
> SOC15_FLUSH_GPU_TLB_NUM_REG_WAIT * 7 +
> @@ -6127,6 +6200,7 @@ static const struct amdgpu_ring_funcs gfx_v11_0_ring_funcs_gfx = {
> 31 + /* DE_META */
> 3 + /* CNTX_CTRL */
> 5 + /* HDP_INVL */
> + 22 + /* SET_Q_PREEMPTION_MODE */
> 8 + 8 + /* FENCE x2 */
> 8, /* gfx_v11_0_emit_mem_sync */
> .emit_ib_size = 4, /* gfx_v11_0_ring_emit_ib_gfx */
> --
> 2.34.1
>
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