bloom: always use a larger minimum size for bloom filter

Increases accuracy at the lower end.

Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/lib/bloom.c b/lib/bloom.c
index fbae80820813a2f548dc54d4d90b97ff1626dbd2..9ab89e4b6f29af482f210f98bd2a088a64d9c416 100644 (file)
--- a/lib/bloom.c
+++ b/lib/bloom.c
@@ -3,6 +3,7 @@
 
 #include "bloom.h"
 #include "../hash.h"
+#include "../minmax.h"
 
 struct bloom {
        uint64_t nentries;
@@ -16,6 +17,8 @@ struct bloom {
 static unsigned int jhash_init[] = { 0, 0x12db635, 0x2a4a53 };
 #define N_HASHES       3
 
+#define MIN_ENTRIES    1073741824UL
+
 struct bloom *bloom_new(uint64_t entries)
 {
        struct bloom *b;
@@ -24,6 +27,7 @@ struct bloom *bloom_new(uint64_t entries)
        b = malloc(sizeof(*b));
        b->nentries = entries;
        no_uints = (entries + BITS_PER_INDEX - 1) / BITS_PER_INDEX;
+       no_uints = max((unsigned long) no_uints, MIN_ENTRIES);
        b->map = calloc(no_uints, sizeof(uint32_t));
        if (!b->map) {
                free(b);