drm/i915/gvt: add a fastpath for cmd parsing on MI_NOOP

MI_NOOP is a common command appearing in almost all command buffers, put it
into a fastpath can improve perfomance, especially in command buffers
contains lots of MI_NOOPs (0s).

Take glmark2 as an example, 3% performance increase is observed after
introduced this patch. Meanwhile, in case where abundant in MI_NOOPs,
up to 12% performance increase is measured.

v2: use lowercase for index of MI_NOOP in cmd_info (zhenyu wang)

Signed-off-by: Li Weinan <weinan.z.li@intel.com>
Signed-off-by: Zhao Yan <yan.y.zhao@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/gvt/cmd_parser.c b/drivers/gpu/drm/i915/gvt/cmd_parser.c
index 0dd88fe2e39a..4ba503ef5d2c 100644
--- a/drivers/gpu/drm/i915/gvt/cmd_parser.c
+++ b/drivers/gpu/drm/i915/gvt/cmd_parser.c
@@ -1817,6 +1817,8 @@ static int cmd_handler_mi_batch_buffer_start(struct parser_exec_state *s)
         return ret;
 }
 
+static int mi_noop_index;
+
 static struct cmd_info cmd_info[] = {
         {"MI_NOOP", OP_MI_NOOP, F_LEN_CONST, R_ALL, D_ALL, 0, 1, NULL},
 
@@ -2502,7 +2504,12 @@ static int cmd_parser_exec(struct parser_exec_state *s)
 
         cmd = cmd_val(s, 0);
 
-        info = get_cmd_info(s->vgpu->gvt, cmd, s->ring_id);
+        /* fastpath for MI_NOOP */
+        if (cmd == MI_NOOP)
+                info = &cmd_info[mi_noop_index];
+        else
+                info = get_cmd_info(s->vgpu->gvt, cmd, s->ring_id);
+
         if (info == NULL) {
                 gvt_vgpu_err("unknown cmd 0x%x, opcode=0x%x, addr_type=%s, ring %d, workload=%p\n",
                                 cmd, get_opcode(cmd, s->ring_id),
@@ -2904,6 +2911,8 @@ static int init_cmd_table(struct intel_gvt *gvt)
                                         info->name);
                         return -EEXIST;
                 }
+                if (cmd_info[i].opcode == OP_MI_NOOP)
+                        mi_noop_index = i;
 
                 INIT_HLIST_NODE(&e->hlist);
                 add_cmd_entry(gvt, e);