From: Anthony Pesch <inolen@gmail.com>
Date: Sat, 18 Jan 2020 05:54:10 +0000 (-0500)
Subject: util/hash_table: replace _mesa_hash_data's fnv1a hash function with xxhash
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=931388ceca323750682604c7b70d355fa00d9900;p=mesa.git

util/hash_table: replace _mesa_hash_data's fnv1a hash function with xxhash

For most key sizes, xxhash outperforms fnv1a's hash rate substantially (bug
2153). In particular, the V3D driver hashes multiple ~200 byte keys as part
of the shader cache lookup which can easily eat up 10-20% of the runtime on
the Raspberry Pi. Swapping over to xxhash drops this to ~1% of the runtime.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3475>
---

diff --git a/src/util/hash_table.c b/src/util/hash_table.c
index 9d982708868..48d59e48431 100644
--- a/src/util/hash_table.c
+++ b/src/util/hash_table.c
@@ -50,6 +50,9 @@
 #include "main/hash.h"
 #include "fast_urem_by_const.h"
 
+#define XXH_INLINE_ALL
+#include "xxhash.h"
+
 static const uint32_t deleted_key_value;
 
 /**
@@ -549,8 +552,7 @@ _mesa_hash_table_random_entry(struct hash_table *ht,
 uint32_t
 _mesa_hash_data(const void *data, size_t size)
 {
-   return _mesa_fnv32_1a_accumulate_block(_mesa_fnv32_1a_offset_bias,
-                                          data, size);
+   return XXH32(data, size, 0);
 }
 
 /** FNV-1a string hash implementation */