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 <ch...@chris-wilson.co.uk>
---
drivers/gpu/drm/i915/i915_cmd_parser.c | 45 +++++++++++++++++++++-------------
1 file changed, 28 insertions(+), 17 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c
b/drivers/gpu/drm/i915/i915_cmd_parser.c
index ea9df2bb87de..7a0250c1d201 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), ~0 << (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
@@ -627,12 +627,24 @@ static bool validate_regs_sorted(struct intel_engine_cs
*ring)
* 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 *ring,
const struct drm_i915_cmd_table *cmd_tables,
@@ -648,7 +660,7 @@ static int init_hash_table(struct intel_engine_cs *ring,
for (j = 0; j < table->count; j++) {
struct drm_i915_cmd_descriptor *desc = &table->table[j];
hash_add(ring->cmd_hash, &desc->node[ring->id],
- desc->cmd.value & CMD_HASH_MASK);
+ cmd_header_key(desc->cmd.value));
}
}
@@ -776,10 +788,9 @@ find_cmd_in_table(struct intel_engine_cs *ring,
const struct drm_i915_cmd_descriptor *desc;
hash_for_each_possible(ring->cmd_hash, desc, node[ring->id],
- cmd_header & CMD_HASH_MASK) {
+ cmd_header_key(cmd_header))
if (((cmd_header ^ desc->cmd.value) & desc->cmd.mask) == 0)
return desc;
- }
return NULL;
}
--
2.6.2
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