diff options
| author | Heikki Linnakangas <heikki.linnakangas@iki.fi> | 2013-09-04 23:14:33 +0300 |
|---|---|---|
| committer | Heikki Linnakangas <heikki.linnakangas@iki.fi> | 2013-09-04 23:14:33 +0300 |
| commit | 375d8526f2900d0c377f44532f6d09ee06531f67 (patch) | |
| tree | 866db5b0ff2a176ff815e80ca2a72c780079bee8 /src/include | |
| parent | cc52d5b33ff5df29de57dcae9322214cfe9c8464 (diff) | |
Keep heavily-contended fields in XLogCtlInsert on different cache lines.
Performance testing shows that if the insertpos_lck spinlock and the fields
that it protects are on the same cache line with other variables that are
frequently accessed, the false sharing can hurt performance a lot. Keep
them apart by adding some padding.
Diffstat (limited to 'src/include')
| -rw-r--r-- | src/include/pg_config_manual.h | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/src/include/pg_config_manual.h b/src/include/pg_config_manual.h index 1d60be2c477..2e6aad1ca56 100644 --- a/src/include/pg_config_manual.h +++ b/src/include/pg_config_manual.h @@ -200,6 +200,17 @@ #endif /* + * Assumed cache line size. This doesn't affect correctness, but can be + * used for low-level optimizations. Currently, this is only used to pad + * some data structures in xlog.c, to ensure that highly-contended fields + * are on different cache lines. Too small a value can hurt performance due + * to false sharing, while the only downside of too large a value is a few + * bytes of wasted memory. The default is 128, which should be large enough + * for all supported platforms. + */ +#define CACHE_LINE_SIZE 128 + +/* *------------------------------------------------------------------------ * The following symbols are for enabling debugging code, not for * controlling user-visible features or resource limits. |