From b68b29bc8feca0eb340cb857ff1d28d4099c7878 Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Tue, 9 Jul 2024 10:27:12 +0900 Subject: [PATCH] Use pgstat_kind_infos to write fixed shared statistics This is similar to 9004abf6206e, but this time for the write part of the stats file. The code is changed so as, rather than referring to individual members of PgStat_Snapshot in an order based on their PgStat_Kind value, a loop based on pgstat_kind_infos is used to retrieve the contents to write from the snapshot structure, for a size of PgStat_KindInfo's shared_data_len. This requires the addition to PgStat_KindInfo of an offset to track the location of each fixed-numbered stats in PgStat_Snapshot. This change is useful to make this area of the code more easily pluggable, and reduces the knowledge of specific fixed-numbered kinds in pgstat.c. Reviewed-by: Bertrand Drouvot Discussion: https://postgr.es/m/Zot5bxoPYdS7yaoy@paquier.xyz --- src/backend/utils/activity/pgstat.c | 56 ++++++++++------------------- src/include/utils/pgstat_internal.h | 6 ++++ 2 files changed, 24 insertions(+), 38 deletions(-) diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c index c37c11b2ecb..65b937a85f4 100644 --- a/src/backend/utils/activity/pgstat.c +++ b/src/backend/utils/activity/pgstat.c @@ -349,6 +349,7 @@ static const PgStat_KindInfo pgstat_kind_infos[PGSTAT_NUM_KINDS] = { .fixed_amount = true, + .snapshot_ctl_off = offsetof(PgStat_Snapshot, archiver), .shared_ctl_off = offsetof(PgStat_ShmemControl, archiver), .shared_data_off = offsetof(PgStatShared_Archiver, stats), .shared_data_len = sizeof(((PgStatShared_Archiver *) 0)->stats), @@ -362,6 +363,7 @@ static const PgStat_KindInfo pgstat_kind_infos[PGSTAT_NUM_KINDS] = { .fixed_amount = true, + .snapshot_ctl_off = offsetof(PgStat_Snapshot, bgwriter), .shared_ctl_off = offsetof(PgStat_ShmemControl, bgwriter), .shared_data_off = offsetof(PgStatShared_BgWriter, stats), .shared_data_len = sizeof(((PgStatShared_BgWriter *) 0)->stats), @@ -375,6 +377,7 @@ static const PgStat_KindInfo pgstat_kind_infos[PGSTAT_NUM_KINDS] = { .fixed_amount = true, + .snapshot_ctl_off = offsetof(PgStat_Snapshot, checkpointer), .shared_ctl_off = offsetof(PgStat_ShmemControl, checkpointer), .shared_data_off = offsetof(PgStatShared_Checkpointer, stats), .shared_data_len = sizeof(((PgStatShared_Checkpointer *) 0)->stats), @@ -388,6 +391,7 @@ static const PgStat_KindInfo pgstat_kind_infos[PGSTAT_NUM_KINDS] = { .fixed_amount = true, + .snapshot_ctl_off = offsetof(PgStat_Snapshot, io), .shared_ctl_off = offsetof(PgStat_ShmemControl, io), .shared_data_off = offsetof(PgStatShared_IO, stats), .shared_data_len = sizeof(((PgStatShared_IO *) 0)->stats), @@ -401,6 +405,7 @@ static const PgStat_KindInfo pgstat_kind_infos[PGSTAT_NUM_KINDS] = { .fixed_amount = true, + .snapshot_ctl_off = offsetof(PgStat_Snapshot, slru), .shared_ctl_off = offsetof(PgStat_ShmemControl, slru), .shared_data_off = offsetof(PgStatShared_SLRU, stats), .shared_data_len = sizeof(((PgStatShared_SLRU *) 0)->stats), @@ -414,6 +419,7 @@ static const PgStat_KindInfo pgstat_kind_infos[PGSTAT_NUM_KINDS] = { .fixed_amount = true, + .snapshot_ctl_off = offsetof(PgStat_Snapshot, wal), .shared_ctl_off = offsetof(PgStat_ShmemControl, wal), .shared_data_off = offsetof(PgStatShared_Wal, stats), .shared_data_len = sizeof(((PgStatShared_Wal *) 0)->stats), @@ -1371,47 +1377,21 @@ pgstat_write_statsfile(void) format_id = PGSTAT_FILE_FORMAT_ID; write_chunk_s(fpout, &format_id); - /* - * XXX: The following could now be generalized to just iterate over - * pgstat_kind_infos instead of knowing about the different kinds of - * stats. - */ + /* Write various stats structs for fixed number of objects */ + for (int kind = PGSTAT_KIND_FIRST_VALID; kind <= PGSTAT_KIND_LAST; kind++) + { + char *ptr; + const PgStat_KindInfo *info = pgstat_get_kind_info(kind); - /* - * Write archiver stats struct - */ - pgstat_build_snapshot_fixed(PGSTAT_KIND_ARCHIVER); - write_chunk_s(fpout, &pgStatLocal.snapshot.archiver); + if (!info->fixed_amount) + continue; - /* - * Write bgwriter stats struct - */ - pgstat_build_snapshot_fixed(PGSTAT_KIND_BGWRITER); - write_chunk_s(fpout, &pgStatLocal.snapshot.bgwriter); + Assert(info->snapshot_ctl_off != 0); - /* - * Write checkpointer stats struct - */ - pgstat_build_snapshot_fixed(PGSTAT_KIND_CHECKPOINTER); - write_chunk_s(fpout, &pgStatLocal.snapshot.checkpointer); - - /* - * Write IO stats struct - */ - pgstat_build_snapshot_fixed(PGSTAT_KIND_IO); - write_chunk_s(fpout, &pgStatLocal.snapshot.io); - - /* - * Write SLRU stats struct - */ - pgstat_build_snapshot_fixed(PGSTAT_KIND_SLRU); - write_chunk_s(fpout, &pgStatLocal.snapshot.slru); - - /* - * Write WAL stats struct - */ - pgstat_build_snapshot_fixed(PGSTAT_KIND_WAL); - write_chunk_s(fpout, &pgStatLocal.snapshot.wal); + pgstat_build_snapshot_fixed(kind); + ptr = ((char *) &pgStatLocal.snapshot) + info->snapshot_ctl_off; + write_chunk(fpout, ptr, info->shared_data_len); + } /* * Walk through the stats entries diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h index e21ef4e2c98..43d6deb03cf 100644 --- a/src/include/utils/pgstat_internal.h +++ b/src/include/utils/pgstat_internal.h @@ -199,6 +199,12 @@ typedef struct PgStat_KindInfo */ uint32 shared_size; + /* + * The offset of the statistics struct in the cached statistics snapshot + * PgStat_Snapshot, for fixed-numbered statistics. + */ + uint32 snapshot_ctl_off; + /* * The offset of the statistics struct in the containing shared memory * control structure PgStat_ShmemControl, for fixed-numbered statistics.