[PATCH 2/2] drm/xe: Waste fewer instructions in emit_wa_job()
Raag Jadav
raag.jadav at intel.com
Fri Jun 27 13:20:10 UTC 2025
On Fri, Jun 27, 2025 at 02:14:38PM +0100, Tvrtko Ursulin wrote:
> I was debugging some unrelated issue and noticed the current code was
> very verbose. We can improve it easily by using the more common batch
> buffer building pattern.
>
> Before:
>
> bb->cs[bb->len++] = MI_LOAD_REGISTER_REG | MI_LRR_DST_CS_MMIO;
> c4d: 41 8b 56 10 mov 0x10(%r14),%edx
> c51: 49 8b 4e 08 mov 0x8(%r14),%rcx
> c55: 8d 72 01 lea 0x1(%rdx),%esi
> c58: 41 89 76 10 mov %esi,0x10(%r14)
> c5c: c7 04 91 01 00 08 15 movl $0x15080001,(%rcx,%rdx,4)
> bb->cs[bb->len++] = entry->reg.addr;
> c63: 8b 08 mov (%rax),%ecx
> c65: 41 8b 56 10 mov 0x10(%r14),%edx
> c69: 49 8b 76 08 mov 0x8(%r14),%rsi
> c6d: 81 e1 ff ff 3f 00 and $0x3fffff,%ecx
> c73: 8d 7a 01 lea 0x1(%rdx),%edi
> c76: 41 89 7e 10 mov %edi,0x10(%r14)
> c7a: 89 0c 96 mov %ecx,(%rsi,%rdx,4)
> ..etc..
>
> After:
>
> *cs++ = MI_LOAD_REGISTER_REG | MI_LRR_DST_CS_MMIO;
> c52: 41 c7 04 24 01 00 08 movl $0x15080001,(%r12)
> c59: 15
> *cs++ = entry->reg.addr;
> c5a: 8b 10 mov (%rax),%edx
> ..etc..
Use bloat-o-meter. It usually provides nice summary.
Raag
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
> ---
> drivers/gpu/drm/xe/xe_gt.c | 77 ++++++++++++++++++++-----------------
> drivers/gpu/drm/xe/xe_lrc.c | 12 +++---
> drivers/gpu/drm/xe/xe_lrc.h | 2 +-
> 3 files changed, 49 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_gt.c b/drivers/gpu/drm/xe/xe_gt.c
> index 86018fee74d3..a5b0db43bcee 100644
> --- a/drivers/gpu/drm/xe/xe_gt.c
> +++ b/drivers/gpu/drm/xe/xe_gt.c
> @@ -182,19 +182,21 @@ static int emit_wa_job(struct xe_gt *gt, struct xe_exec_queue *q)
> {
> struct xe_reg_sr *sr = &q->hwe->reg_lrc;
> struct xe_reg_sr_entry *entry;
> + int count = 0, count_rmw = 0;
> + struct xe_sched_job *job;
> + struct dma_fence *fence;
> unsigned long idx;
> - struct xe_sched_job *job;
> struct xe_bb *bb;
> - struct dma_fence *fence;
> long timeout;
> - int count_rmw = 0;
> - int count = 0;
> + u32 *cs;
>
> /* Just pick a large BB size */
> bb = xe_bb_new(gt, xe_gt_lrc_size(gt, q->hwe->class), false);
> if (IS_ERR(bb))
> return PTR_ERR(bb);
>
> + cs = bb->cs;
> +
> /* count RMW registers as those will be handled separately */
> xa_for_each(&sr->xa, idx, entry) {
> if (entry->reg.masked || entry->clr_bits == ~0)
> @@ -209,7 +211,7 @@ static int emit_wa_job(struct xe_gt *gt, struct xe_exec_queue *q)
> if (count) {
> /* emit single LRI with all non RMW regs */
>
> - bb->cs[bb->len++] = MI_LOAD_REGISTER_IMM | MI_LRI_NUM_REGS(count);
> + *cs++ = MI_LOAD_REGISTER_IMM | MI_LRI_NUM_REGS(count);
>
> xa_for_each(&sr->xa, idx, entry) {
> struct xe_reg reg = entry->reg;
> @@ -224,8 +226,8 @@ static int emit_wa_job(struct xe_gt *gt, struct xe_exec_queue *q)
>
> val |= entry->set_bits;
>
> - bb->cs[bb->len++] = reg.addr;
> - bb->cs[bb->len++] = val;
> + *cs++ = reg.addr;
> + *cs++ = val;
> xe_gt_dbg(gt, "REG[0x%x] = 0x%08x", reg.addr, val);
> }
> }
> @@ -237,46 +239,49 @@ static int emit_wa_job(struct xe_gt *gt, struct xe_exec_queue *q)
> if (entry->reg.masked || entry->clr_bits == ~0)
> continue;
>
> - bb->cs[bb->len++] = MI_LOAD_REGISTER_REG | MI_LRR_DST_CS_MMIO;
> - bb->cs[bb->len++] = entry->reg.addr;
> - bb->cs[bb->len++] = CS_GPR_REG(0, 0).addr;
> + *cs++ = MI_LOAD_REGISTER_REG | MI_LRR_DST_CS_MMIO;
> + *cs++ = entry->reg.addr;
> + *cs++ = CS_GPR_REG(0, 0).addr;
>
> - bb->cs[bb->len++] = MI_LOAD_REGISTER_IMM | MI_LRI_NUM_REGS(2) |
> - MI_LRI_LRM_CS_MMIO;
> - bb->cs[bb->len++] = CS_GPR_REG(0, 1).addr;
> - bb->cs[bb->len++] = entry->clr_bits;
> - bb->cs[bb->len++] = CS_GPR_REG(0, 2).addr;
> - bb->cs[bb->len++] = entry->set_bits;
> + *cs++ = MI_LOAD_REGISTER_IMM | MI_LRI_NUM_REGS(2) |
> + MI_LRI_LRM_CS_MMIO;
> + *cs++ = CS_GPR_REG(0, 1).addr;
> + *cs++ = entry->clr_bits;
> + *cs++ = CS_GPR_REG(0, 2).addr;
> + *cs++ = entry->set_bits;
>
> - bb->cs[bb->len++] = MI_MATH(8);
> - bb->cs[bb->len++] = CS_ALU_INSTR_LOAD(SRCA, REG0);
> - bb->cs[bb->len++] = CS_ALU_INSTR_LOADINV(SRCB, REG1);
> - bb->cs[bb->len++] = CS_ALU_INSTR_AND;
> - bb->cs[bb->len++] = CS_ALU_INSTR_STORE(REG0, ACCU);
> - bb->cs[bb->len++] = CS_ALU_INSTR_LOAD(SRCA, REG0);
> - bb->cs[bb->len++] = CS_ALU_INSTR_LOAD(SRCB, REG2);
> - bb->cs[bb->len++] = CS_ALU_INSTR_OR;
> - bb->cs[bb->len++] = CS_ALU_INSTR_STORE(REG0, ACCU);
> + *cs++ = MI_MATH(8);
> + *cs++ = CS_ALU_INSTR_LOAD(SRCA, REG0);
> + *cs++ = CS_ALU_INSTR_LOADINV(SRCB, REG1);
> + *cs++ = CS_ALU_INSTR_AND;
> + *cs++ = CS_ALU_INSTR_STORE(REG0, ACCU);
> + *cs++ = CS_ALU_INSTR_LOAD(SRCA, REG0);
> + *cs++ = CS_ALU_INSTR_LOAD(SRCB, REG2);
> + *cs++ = CS_ALU_INSTR_OR;
> + *cs++ = CS_ALU_INSTR_STORE(REG0, ACCU);
>
> - bb->cs[bb->len++] = MI_LOAD_REGISTER_REG | MI_LRR_SRC_CS_MMIO;
> - bb->cs[bb->len++] = CS_GPR_REG(0, 0).addr;
> - bb->cs[bb->len++] = entry->reg.addr;
> + *cs++ = MI_LOAD_REGISTER_REG | MI_LRR_SRC_CS_MMIO;
> + *cs++ = CS_GPR_REG(0, 0).addr;
> + *cs++ = entry->reg.addr;
>
> xe_gt_dbg(gt, "REG[%#x] = ~%#x|%#x\n",
> entry->reg.addr, entry->clr_bits, entry->set_bits);
> }
>
> /* reset used GPR */
> - bb->cs[bb->len++] = MI_LOAD_REGISTER_IMM | MI_LRI_NUM_REGS(3) | MI_LRI_LRM_CS_MMIO;
> - bb->cs[bb->len++] = CS_GPR_REG(0, 0).addr;
> - bb->cs[bb->len++] = 0;
> - bb->cs[bb->len++] = CS_GPR_REG(0, 1).addr;
> - bb->cs[bb->len++] = 0;
> - bb->cs[bb->len++] = CS_GPR_REG(0, 2).addr;
> - bb->cs[bb->len++] = 0;
> + *cs++ = MI_LOAD_REGISTER_IMM | MI_LRI_NUM_REGS(3) |
> + MI_LRI_LRM_CS_MMIO;
> + *cs++ = CS_GPR_REG(0, 0).addr;
> + *cs++ = 0;
> + *cs++ = CS_GPR_REG(0, 1).addr;
> + *cs++ = 0;
> + *cs++ = CS_GPR_REG(0, 2).addr;
> + *cs++ = 0;
> }
>
> - xe_lrc_emit_hwe_state_instructions(q, bb);
> + cs = xe_lrc_emit_hwe_state_instructions(q, cs);
> +
> + bb->len = cs - bb->cs;
>
> job = xe_bb_create_job(q, bb);
> if (IS_ERR(job)) {
> diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
> index 37598588a54f..8780ea1340d0 100644
> --- a/drivers/gpu/drm/xe/xe_lrc.c
> +++ b/drivers/gpu/drm/xe/xe_lrc.c
> @@ -1775,7 +1775,7 @@ static const struct instr_state xe_hpg_svg_state[] = {
> { .instr = CMD_3DSTATE_DRAWING_RECTANGLE, .num_dw = 4 },
> };
>
> -void xe_lrc_emit_hwe_state_instructions(struct xe_exec_queue *q, struct xe_bb *bb)
> +u32 *xe_lrc_emit_hwe_state_instructions(struct xe_exec_queue *q, u32 *cs)
> {
> struct xe_gt *gt = q->hwe->gt;
> struct xe_device *xe = gt_to_xe(gt);
> @@ -1810,7 +1810,7 @@ void xe_lrc_emit_hwe_state_instructions(struct xe_exec_queue *q, struct xe_bb *b
> if (!state_table) {
> xe_gt_dbg(gt, "No non-register state to emit on graphics ver %d.%02d\n",
> GRAPHICS_VER(xe), GRAPHICS_VERx100(xe) % 100);
> - return;
> + return cs;
> }
>
> for (int i = 0; i < state_table_size; i++) {
> @@ -1833,12 +1833,14 @@ void xe_lrc_emit_hwe_state_instructions(struct xe_exec_queue *q, struct xe_bb *b
> instr == CMD_3DSTATE_DRAWING_RECTANGLE)
> instr = CMD_3DSTATE_DRAWING_RECTANGLE_FAST;
>
> - bb->cs[bb->len] = instr;
> + *cs = instr;
> if (!is_single_dw)
> - bb->cs[bb->len] |= (num_dw - 2);
> + *cs |= (num_dw - 2);
>
> - bb->len += num_dw;
> + cs += num_dw;
> }
> +
> + return cs;
> }
>
> struct xe_lrc_snapshot *xe_lrc_snapshot_capture(struct xe_lrc *lrc)
> diff --git a/drivers/gpu/drm/xe/xe_lrc.h b/drivers/gpu/drm/xe/xe_lrc.h
> index eb6e8de8c939..b6c8053c581b 100644
> --- a/drivers/gpu/drm/xe/xe_lrc.h
> +++ b/drivers/gpu/drm/xe/xe_lrc.h
> @@ -112,7 +112,7 @@ void xe_lrc_dump_default(struct drm_printer *p,
> struct xe_gt *gt,
> enum xe_engine_class);
>
> -void xe_lrc_emit_hwe_state_instructions(struct xe_exec_queue *q, struct xe_bb *bb);
> +u32 *xe_lrc_emit_hwe_state_instructions(struct xe_exec_queue *q, u32 *cs);
>
> struct xe_lrc_snapshot *xe_lrc_snapshot_capture(struct xe_lrc *lrc);
> void xe_lrc_snapshot_capture_delayed(struct xe_lrc_snapshot *snapshot);
> --
> 2.48.0
>
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