From d6a4ead7a38666b9acdb098012a178c4c4950eca Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 18 Aug 2016 17:17:14 +0100 Subject: [PATCH] drm/i915/cmdparser: Improve hash function The existing code's hashfunction is very suboptimal (most 3D commands use the same bucket degrading the hash to a long list). The code even acknowledge that the issue was known and the fix simple: /* * If we attempt to generate a perfect hash, we should be able to look at bits * 31:29 of a command from a batch buffer and use the full mask for that * client. The existing INSTR_CLIENT_MASK/SHIFT defines can be used for this. */ Signed-off-by: Chris Wilson Reviewed-by: Matthew Auld Link: http://patchwork.freedesktop.org/patch/msgid/20160818161718.27187-35-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_cmd_parser.c | 51 +++++++++++++++++++++------------- 1 file changed, 31 insertions(+), 20 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c index d1858f8..54aeab3 100644 --- a/drivers/gpu/drm/i915/i915_cmd_parser.c +++ b/drivers/gpu/drm/i915/i915_cmd_parser.c @@ -86,24 +86,24 @@ * general bitmasking mechanism. */ -#define STD_MI_OPCODE_MASK 0xFF800000 -#define STD_3D_OPCODE_MASK 0xFFFF0000 -#define STD_2D_OPCODE_MASK 0xFFC00000 -#define STD_MFX_OPCODE_MASK 0xFFFF0000 +#define STD_MI_OPCODE_SHIFT (32 - 9) +#define STD_3D_OPCODE_SHIFT (32 - 16) +#define STD_2D_OPCODE_SHIFT (32 - 10) +#define STD_MFX_OPCODE_SHIFT (32 - 16) #define CMD(op, opm, f, lm, fl, ...) \ { \ .flags = (fl) | ((f) ? CMD_DESC_FIXED : 0), \ - .cmd = { (op), (opm) }, \ + .cmd = { (op), ~0u << (opm) }, \ .length = { (lm) }, \ __VA_ARGS__ \ } /* Convenience macros to compress the tables */ -#define SMI STD_MI_OPCODE_MASK -#define S3D STD_3D_OPCODE_MASK -#define S2D STD_2D_OPCODE_MASK -#define SMFX STD_MFX_OPCODE_MASK +#define SMI STD_MI_OPCODE_SHIFT +#define S3D STD_3D_OPCODE_SHIFT +#define S2D STD_2D_OPCODE_SHIFT +#define SMFX STD_MFX_OPCODE_SHIFT #define F true #define S CMD_DESC_SKIP #define R CMD_DESC_REJECT @@ -696,12 +696,26 @@ struct cmd_node { * non-opcode bits being set. But if we don't include those bits, some 3D * commands may hash to the same bucket due to not including opcode bits that * make the command unique. For now, we will risk hashing to the same bucket. - * - * If we attempt to generate a perfect hash, we should be able to look at bits - * 31:29 of a command from a batch buffer and use the full mask for that - * client. The existing INSTR_CLIENT_MASK/SHIFT defines can be used for this. */ -#define CMD_HASH_MASK STD_MI_OPCODE_MASK +static inline u32 cmd_header_key(u32 x) +{ + u32 shift; + + switch (x >> INSTR_CLIENT_SHIFT) { + default: + case INSTR_MI_CLIENT: + shift = STD_MI_OPCODE_SHIFT; + break; + case INSTR_RC_CLIENT: + shift = STD_3D_OPCODE_SHIFT; + break; + case INSTR_BC_CLIENT: + shift = STD_2D_OPCODE_SHIFT; + break; + } + + return x >> shift; +} static int init_hash_table(struct intel_engine_cs *engine, const struct drm_i915_cmd_table *cmd_tables, @@ -725,7 +739,7 @@ static int init_hash_table(struct intel_engine_cs *engine, desc_node->desc = desc; hash_add(engine->cmd_hash, &desc_node->node, - desc->cmd.value & CMD_HASH_MASK); + cmd_header_key(desc->cmd.value)); } } @@ -859,12 +873,9 @@ find_cmd_in_table(struct intel_engine_cs *engine, struct cmd_node *desc_node; hash_for_each_possible(engine->cmd_hash, desc_node, node, - cmd_header & CMD_HASH_MASK) { + cmd_header_key(cmd_header)) { const struct drm_i915_cmd_descriptor *desc = desc_node->desc; - u32 masked_cmd = desc->cmd.mask & cmd_header; - u32 masked_value = desc->cmd.value & desc->cmd.mask; - - if (masked_cmd == masked_value) + if (((cmd_header ^ desc->cmd.value) & desc->cmd.mask) == 0) return desc; } -- 2.7.4