From 06d3fc9cda850e496170b1d02d321ef0d606a4f7 Mon Sep 17 00:00:00 2001 From: Melanie Plageman Date: Wed, 24 Nov 2021 11:39:48 -0500 Subject: [PATCH v15 4/7] Add "buffers" to pgstat_reset_shared_counters Backends count IO operations for various IO paths in their PgBackendStatus. Upon exit, they send these counts to the stats collector. Prior to this commit, these IO Ops stats would have been reset when the target was "bgwriter". With this commit, target "bgwriter" no longer will cause the IO operations stats to be reset, and the IO operations stats can be reset with new target, "buffers". --- doc/src/sgml/monitoring.sgml | 2 +- src/backend/postmaster/pgstat.c | 67 +++++++++++++++++++-- src/backend/utils/activity/backend_status.c | 27 +++++++++ src/include/pgstat.h | 12 +++- src/include/utils/backend_status.h | 2 + 5 files changed, 103 insertions(+), 7 deletions(-) diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index af6914872b..d4dd5d3623 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -3473,7 +3473,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i stats_reset timestamp with time zone - Time at which these statistics were last reset + Time at which these statistics were last reset. diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index aa538d175f..0d18a4dc02 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -1435,6 +1435,28 @@ pgstat_reset_counters(void) pgstat_send(&msg, sizeof(msg)); } +/* + * Helper function to collect and send live backends' current IO operations + * stats counters when a stats reset is initiated so that they may be deducted + * from future totals. + */ +static void +pgstat_send_buffers_reset(PgStat_MsgResetsharedcounter *msg) +{ + int backend_type; + PgStatIOPathOps ops[BACKEND_NUM_TYPES]; + + memset(ops, 0, sizeof(ops)); + pgstat_report_live_backend_io_path_ops(ops); + + for (backend_type = 1; backend_type < BACKEND_NUM_TYPES; backend_type++) + { + msg->m_backend_resets.backend_type = backend_type; + memcpy(&msg->m_backend_resets.iop, &ops[backend_type], sizeof(msg->m_backend_resets.iop)); + pgstat_send(msg, sizeof(PgStat_MsgResetsharedcounter)); + } +} + /* ---------- * pgstat_reset_shared_counters() - * @@ -1452,7 +1474,14 @@ pgstat_reset_shared_counters(const char *target) if (pgStatSock == PGINVALID_SOCKET) return; - if (strcmp(target, "archiver") == 0) + pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSHAREDCOUNTER); + if (strcmp(target, "buffers") == 0) + { + msg.m_resettarget = RESET_BUFFERS; + pgstat_send_buffers_reset(&msg); + return; + } + else if (strcmp(target, "archiver") == 0) msg.m_resettarget = RESET_ARCHIVER; else if (strcmp(target, "bgwriter") == 0) msg.m_resettarget = RESET_BGWRITER; @@ -1464,8 +1493,9 @@ pgstat_reset_shared_counters(const char *target) errmsg("unrecognized reset target: \"%s\"", target), errhint("Target must be \"archiver\", \"bgwriter\", or \"wal\"."))); - pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSHAREDCOUNTER); + pgstat_send(&msg, sizeof(msg)); + } /* ---------- @@ -5285,10 +5315,39 @@ pgstat_recv_resetsharedcounter(PgStat_MsgResetsharedcounter *msg, int len) { if (msg->m_resettarget == RESET_BGWRITER) { - /* Reset the global, bgwriter and checkpointer statistics for the cluster. */ - memset(&globalStats, 0, sizeof(globalStats)); + /* + * Reset the global, bgwriter and checkpointer statistics for the + * cluster. + */ + memset(&globalStats.checkpointer, 0, sizeof(globalStats.checkpointer)); + memset(&globalStats.bgwriter, 0, sizeof(globalStats.bgwriter)); globalStats.bgwriter.stat_reset_timestamp = GetCurrentTimestamp(); } + else if (msg->m_resettarget == RESET_BUFFERS) + { + /* + * Because the stats collector cannot write to live backends' + * PgBackendStatuses, it maintains an array of "resets". The reset + * message contains the current values of these counters for live + * backends. The stats collector saves these in its "resets" array, + * then zeroes out the exited backends' saved IO op counters. This is + * required to calculate an accurate total for each IO op counter post + * reset. + */ + BackendType backend_type = msg->m_backend_resets.backend_type; + + /* + * Though globalStats.buffers only needs to be reset once, doing so for + * every message is less brittle and the extra cost is irrelevant given + * how often stats are reset. + */ + memset(&globalStats.buffers.ops, 0, sizeof(globalStats.buffers.ops)); + globalStats.buffers.stat_reset_timestamp = GetCurrentTimestamp(); + + memcpy(&globalStats.buffers.resets[backend_type], + &msg->m_backend_resets.iop.io_path_ops, sizeof(msg->m_backend_resets.iop.io_path_ops)); + + } else if (msg->m_resettarget == RESET_ARCHIVER) { /* Reset the archiver statistics for the cluster. */ diff --git a/src/backend/utils/activity/backend_status.c b/src/backend/utils/activity/backend_status.c index 0683f243dc..1617033e26 100644 --- a/src/backend/utils/activity/backend_status.c +++ b/src/backend/utils/activity/backend_status.c @@ -631,6 +631,33 @@ pgstat_report_activity(BackendState state, const char *cmd_str) PGSTAT_END_WRITE_ACTIVITY(beentry); } +/* + * Iterate through BackendStatusArray and capture live backends' stats on IO + * Ops for all IO Paths, adding them to that backend type's member of the + * backend_io_path_ops structure. + */ +void +pgstat_report_live_backend_io_path_ops(PgStatIOPathOps *backend_io_path_ops) +{ + int i; + PgBackendStatus *beentry = BackendStatusArray; + + /* + * Loop through live backends and capture reset values + */ + for (i = 0; i < MaxBackends + NUM_AUXPROCTYPES; i++) + { + beentry++; + /* Don't count dead backends. They should already be counted */ + if (beentry->st_procpid == 0) + continue; + + pgstat_sum_io_path_ops(backend_io_path_ops[beentry->st_backendType].io_path_ops, + (IOOps *) beentry->io_path_stats); + + } +} + /* -------- * pgstat_report_query_id() - * diff --git a/src/include/pgstat.h b/src/include/pgstat.h index aeb6f52fdd..8c291f1f0d 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -139,6 +139,7 @@ typedef enum PgStat_Shared_Reset_Target { RESET_ARCHIVER, RESET_BGWRITER, + RESET_BUFFERS, RESET_WAL } PgStat_Shared_Reset_Target; @@ -353,7 +354,8 @@ typedef struct PgStatIOPathOps /* * Sent by a backend to the stats collector to report all IO Ops for all IO - * Paths for a given type of a backend. This will happen when the backend exits. + * Paths for a given type of a backend. This will happen when the backend exits + * or when stats are reset. */ typedef struct PgStat_MsgIOPathOps { @@ -365,13 +367,18 @@ typedef struct PgStat_MsgIOPathOps /* * Structure used by stats collector to keep track of all types of exited - * backends' IO Ops for all IO Paths. + * backends' IO Ops for all IO Paths as well as all stats from live backends at + * the time of stats reset. resets is populated using a reset message sent to + * the stats collector. */ typedef struct PgStat_BackendIOPathOps { + TimestampTz stat_reset_timestamp; PgStatIOPathOps ops[BACKEND_NUM_TYPES]; + PgStatIOPathOps resets[BACKEND_NUM_TYPES]; } PgStat_BackendIOPathOps; + /* ---------- * PgStat_MsgResetcounter Sent by the backend to tell the collector * to reset counters @@ -392,6 +399,7 @@ typedef struct PgStat_MsgResetsharedcounter { PgStat_MsgHdr m_hdr; PgStat_Shared_Reset_Target m_resettarget; + PgStat_MsgIOPathOps m_backend_resets; } PgStat_MsgResetsharedcounter; /* ---------- diff --git a/src/include/utils/backend_status.h b/src/include/utils/backend_status.h index 717f58d4cc..9c997cace8 100644 --- a/src/include/utils/backend_status.h +++ b/src/include/utils/backend_status.h @@ -343,6 +343,7 @@ extern void pgstat_bestart(void); extern void pgstat_clear_backend_activity_snapshot(void); /* Activity reporting functions */ +typedef struct PgStatIOPathOps PgStatIOPathOps; static inline void pgstat_inc_ioop(IOOp io_op, IOPath io_path) @@ -370,6 +371,7 @@ pgstat_inc_ioop(IOOp io_op, IOPath io_path) } } extern void pgstat_report_activity(BackendState state, const char *cmd_str); +extern void pgstat_report_live_backend_io_path_ops(PgStatIOPathOps *backend_io_path_ops); extern void pgstat_report_query_id(uint64 query_id, bool force); extern void pgstat_report_tempfile(size_t filesize); extern void pgstat_report_appname(const char *appname); -- 2.32.0