From 43c29e1f449d596ed92f12cc19e41d9731ec3312 Mon Sep 17 00:00:00 2001 From: Changbin Du Date: Thu, 6 Apr 2017 10:55:55 +0800 Subject: [PATCH] drm/i915/gvt: remove redundant ring id check which cause significant CPU misprediction From perf data, found a significant overhead at ring id check in the function get_opcode. This inline function is frequently used. Since Intel static predictor will predict the branch to fall through so the prediction most fail. This is wasting CPU pipeline resource. We do not need check the engine id everywhere, it should be reliable. Signed-off-by: Changbin Du Signed-off-by: Zhenyu Wang --- drivers/gpu/drm/i915/gvt/cmd_parser.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/drivers/gpu/drm/i915/gvt/cmd_parser.c b/drivers/gpu/drm/i915/gvt/cmd_parser.c index 94f2e701e4d4..1abd153bec28 100644 --- a/drivers/gpu/drm/i915/gvt/cmd_parser.c +++ b/drivers/gpu/drm/i915/gvt/cmd_parser.c @@ -616,9 +616,6 @@ static inline u32 get_opcode(u32 cmd, int ring_id) { struct decode_info *d_info; - if (ring_id >= I915_NUM_ENGINES) - return INVALID_OP; - d_info = ring_decode_info[ring_id][CMD_TYPE(cmd)]; if (d_info == NULL) return INVALID_OP; @@ -661,9 +658,6 @@ static inline void print_opcode(u32 cmd, int ring_id) struct decode_info *d_info; int i; - if (ring_id >= I915_NUM_ENGINES) - return; - d_info = ring_decode_info[ring_id][CMD_TYPE(cmd)]; if (d_info == NULL) return; -- 2.20.1