Preallocate hash tables when the number of inserts are known in advance
This avoids unnecessary re-allocations and reinsertions. On webkit.git (i.e. about 182k inserts to the name hash table), this reduces about 100ms out of 3s user time. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Nguyễn Thái Ngọc Duy committed
Mar 17, 2013 at 10:28 UTC
c73592812d36ccc7eccfd0489177970d246fa522
3 files changed
+10
diffcore-rename.c
+1
@@ -389,6 +389,7 @@ static int find_exact_renames(struct diff_options *options)
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struct hash_table file_table;
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init_hash(&file_table);
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+ preallocate_hash(&file_table, rename_src_nr + rename_dst_nr);
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for (i = 0; i < rename_src_nr; i++)
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insert_file_table(&file_table, -1, i, rename_src[i].p->one);
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hash.h
+7
@@ -40,4 +40,11 @@ static inline void init_hash(struct hash_table *table)
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table->array = NULL;
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}
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+static inline void preallocate_hash(struct hash_table *table, unsigned int elts)
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+{
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+ assert(table->size == 0 && table->nr == 0 && table->array == NULL);
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+ table->size = elts * 2;
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+ table->array = xcalloc(sizeof(struct hash_table_entry), table->size);
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+}
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+
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#endif
name-hash.c
+2
@@ -92,6 +92,8 @@ static void lazy_init_name_hash(struct index_state *istate)
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if (istate->name_hash_initialized)
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return;
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+ if (istate->cache_nr)
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+ preallocate_hash(&istate->name_hash, istate->cache_nr);
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for (nr = 0; nr < istate->cache_nr; nr++)
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hash_index_entry(istate, istate->cache[nr]);
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istate->name_hash_initialized = 1;