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mempool: make num_shards a power of 2

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Signed-off-by: Sage Weil <sage@redhat.com>
This commit is contained in:
Sage Weil 2016-10-11 18:17:41 -04:00
parent 735be3662f
commit b174694493
1 changed files with 7 additions and 2 deletions
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9
src/include/mempool.h
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@ -213,7 +213,12 @@ struct list_member_t {
// we shard pool stats across many shard_t's to reduce the amount
// of cacheline ping pong.
enum { num_shards = 64 };
enum {
num_shard_bits = 5
};
enum {
num_shards = 1 << num_shard_bits
};
struct shard_t {
std::atomic<size_t> bytes = {0};
@ -277,7 +282,7 @@ public:
// Dirt cheap, see:
// http://fossies.org/dox/glibc-2.24/pthread__self_8c_source.html
size_t me = (size_t)pthread_self();
size_t i = (me >> 3) % num_shards;
size_t i = (me >> 3) & ((1 << num_shard_bits) - 1);
return &shard[i];
}