diff options
| -rw-r--r-- | src/backend/postmaster/pgstat.c | 10 | ||||
| -rw-r--r-- | src/include/pgstat.h | 10 |
2 files changed, 16 insertions, 4 deletions
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index b5ce2f6cc75..d251fddc0b6 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -330,6 +330,16 @@ pgstat_init(void) #define TESTBYTEVAL ((char) 199) /* + * This static assertion verifies that we didn't mess up the calculations + * involved in selecting maximum payload sizes for our UDP messages. + * Because the only consequence of overrunning PGSTAT_MAX_MSG_SIZE would + * be silent performance loss from fragmentation, it seems worth having a + * compile-time cross-check that we didn't. + */ + StaticAssertStmt(sizeof(PgStat_Msg) <= PGSTAT_MAX_MSG_SIZE, + 'maximum stats message size exceeds PGSTAT_MAX_MSG_SIZE'); + + /* * Create the UDP socket for sending and receiving statistic messages */ hints.ai_flags = AI_PASSIVE; diff --git a/src/include/pgstat.h b/src/include/pgstat.h index fb242e4b91b..b79a0ebcc3f 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -177,11 +177,13 @@ typedef struct PgStat_MsgHdr /* ---------- * Space available in a message. This will keep the UDP packets below 1K, - * which should fit unfragmented into the MTU of the lo interface on most - * platforms. Does anybody care for platforms where it doesn't? + * which should fit unfragmented into the MTU of the loopback interface. + * (Larger values of PGSTAT_MAX_MSG_SIZE would work for that on most + * platforms, but we're being conservative here.) * ---------- */ -#define PGSTAT_MSG_PAYLOAD (1000 - sizeof(PgStat_MsgHdr)) +#define PGSTAT_MAX_MSG_SIZE 1000 +#define PGSTAT_MSG_PAYLOAD (PGSTAT_MAX_MSG_SIZE - sizeof(PgStat_MsgHdr)) /* ---------- @@ -225,7 +227,7 @@ typedef struct PgStat_TableEntry * ---------- */ #define PGSTAT_NUM_TABENTRIES \ - ((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - 3 * sizeof(int)) \ + ((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - 3 * sizeof(int) - 2 * sizeof(PgStat_Counter)) \ / sizeof(PgStat_TableEntry)) typedef struct PgStat_MsgTabstat |