[Mesa-dev] [PATCH 4/7] nir/phi_builder: Use slab allocator for temporary data structures

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

This pass allocates a large number of two different data structures.
This data only lives during the pass.  Use the slab allocator to reduce
the memory overhead (from 5 pointers + possible padding per allocation
to nearly zero per allocation) and potentially improve performance.

NOTE: I have not measured the performace delta across this patch
individually.

Changes in peak memory usage according to Valgrind massif:

mean soft fp64 using uint64:   1,343,998,123 => 1,343,998,123
gfxbench5 aztec ruins high 11:    62,415,414 =>    62,415,414
deus ex mankind divided 148:      62,317,965 =>    62,317,965
deus ex mankind divided 2890:     72,585,466 =>    72,603,614
dirt showdown 676:                75,203,703 =>    72,450,311
dolphin ubershaders 210:          83,185,248 =>    81,041,040

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
---
 src/compiler/nir/nir_phi_builder.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/compiler/nir/nir_phi_builder.c b/src/compiler/nir/nir_phi_builder.c
index 36ab9888f48..4d4d81fcd59 100644
--- a/src/compiler/nir/nir_phi_builder.c
+++ b/src/compiler/nir/nir_phi_builder.c
@@ -23,6 +23,7 @@
 
 #include "nir_phi_builder.h"
 #include "nir/nir_vla.h"
+#include "util/slab.h"
 
 struct nir_phi_builder {
    nir_shader *shader;
@@ -60,6 +61,8 @@ struct nir_phi_builder {
     *    one of the defs provided by nir_phi_builder_value_set_blocK_def().
     */
    struct hash_table *value_block_def_hash;
+   struct slab_mempool value_pool;
+   struct slab_mempool key_pool;
 };
 
 #define NEEDS_PHI ((nir_ssa_def *)(intptr_t)-1)
@@ -134,6 +137,11 @@ nir_phi_builder_create(nir_function_impl *impl)
                                                       phi_builder_key_hash,
                                                       phi_builder_key_equals);
 
+   slab_create(&pb->value_pool, sizeof(struct nir_phi_builder_value),
+               (16 * 1024 - sizeof(void *)) / sizeof(struct nir_phi_builder_value));
+   slab_create(&pb->key_pool, sizeof(struct phi_builder_key),
+               (16 * 1024 - sizeof(void *)) / sizeof(struct phi_builder_key));
+
    return pb;
 }
 
@@ -144,7 +152,7 @@ nir_phi_builder_add_value(struct nir_phi_builder *pb, unsigned num_components,
    struct nir_phi_builder_value *val;
    unsigned i, w_start = 0, w_end = 0;
 
-   val = rzalloc_size(pb, sizeof(*val));
+   val = slab_alloc_st(&pb->value_pool);
    val->builder = pb;
    val->num_components = num_components;
    val->bit_size = bit_size;
@@ -211,7 +219,7 @@ nir_phi_builder_value_set_block_def(struct nir_phi_builder_value *val,
    if (he != NULL) {
       he->data = def;
    } else {
-      struct phi_builder_key *kp = ralloc(val->builder, struct phi_builder_key);
+      struct phi_builder_key *kp = slab_alloc_st(&val->builder->key_pool);
 
       kp->val = k.val;
       kp->block_index = k.block_index;
@@ -362,5 +370,9 @@ nir_phi_builder_finish(struct nir_phi_builder *pb)
       }
    }
 
+   slab_flush_st(&pb->value_pool);
+   slab_flush_st(&pb->key_pool);
+   slab_destroy(&pb->value_pool);
+   slab_destroy(&pb->key_pool);
    ralloc_free(pb);
 }
-- 
2.14.4