diff options
| -rw-r--r-- | include/jemalloc/internal/edata.h | 35 |
1 files changed, 19 insertions, 16 deletions
diff --git a/include/jemalloc/internal/edata.h b/include/jemalloc/internal/edata.h index e77a55e6..d2d16c46 100644 --- a/include/jemalloc/internal/edata.h +++ b/include/jemalloc/internal/edata.h @@ -664,13 +664,20 @@ edata_cmp_summary_get(const edata_t *edata) { static inline int edata_cmp_summary_comp(edata_cmp_summary_t a, edata_cmp_summary_t b) { - int ret; - ret = (a.sn > b.sn) - (a.sn < b.sn); - if (ret != 0) { - return ret; - } - ret = (a.addr > b.addr) - (a.addr < b.addr); - return ret; + /* + * Logically, what we're doing here is comparing based on `.sn`, and + * falling back to comparing on `.addr` in the case that `a.sn == b.sn`. + * We accomplish this by multiplying the result of the `.sn` comparison + * by 2, so that so long as it is not 0, it will dominate the `.addr` + * comparison in determining the sign of the returned result value. + * The justification for doing things this way is that this is + * branchless - all of the branches that would be present in a + * straightforward implementation are common cases, and thus the branch + * prediction accuracy is not great. As a result, this implementation + * is measurably faster (by around 30%). + */ + return (2 * ((a.sn > b.sn) - (a.sn < b.sn))) + + ((a.addr > b.addr) - (a.addr < b.addr)); } static inline int @@ -683,15 +690,11 @@ edata_snad_comp(const edata_t *a, const edata_t *b) { static inline int edata_esnead_comp(const edata_t *a, const edata_t *b) { - int ret; - - ret = edata_esn_comp(a, b); - if (ret != 0) { - return ret; - } - - ret = edata_ead_comp(a, b); - return ret; + /* + * Similar to `edata_cmp_summary_comp`, we've opted for a + * branchless implementation for the sake of performance. + */ + return (2 * edata_esn_comp(a, b)) + edata_ead_comp(a, b); } ph_proto(, edata_avail, edata_t) |