From 1b9f9b97d5ca74532620cb51c8f8beb23500537f Mon Sep 17 00:00:00 2001 From: David Geier Date: Fri, 5 Dec 2025 08:58:18 +0100 Subject: [PATCH v3 3/3] Add GUC --- src/backend/postmaster/postmaster.c | 11 +++++++++ src/backend/tcop/postgres.c | 11 +++++++++ src/backend/utils/init/postinit.c | 3 --- src/backend/utils/misc/guc_parameters.dat | 7 ++++++ src/backend/utils/misc/guc_tables.c | 10 +++++++++ src/bin/pg_test_timing/pg_test_timing.c | 2 +- src/bin/pgbench/pgbench.c | 2 +- src/bin/psql/startup.c | 2 +- src/common/instr_time.c | 11 +++++++++ src/include/portability/instr_time.h | 27 +++++++++++++---------- src/include/utils/guc_tables.h | 1 + 11 files changed, 69 insertions(+), 18 deletions(-) diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index 921d73226d6..a6dfaf356ee 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -1005,6 +1005,17 @@ PostmasterMain(int argc, char *argv[]) */ CreateSharedMemoryAndSemaphores(); + /* + * Initialize high-precision interval timing. + * Raise FATAL error if RDTSC is requested but not available. + */ + INSTR_TIME_INITIALIZE(true); + +#if defined(__x86_64__) && defined(__linux__) + if (fast_clock_source == FAST_CLOCK_SOURCE_RDTSC && (!has_rdtsc || !has_rdtscp)) + ereport(FATAL, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("TSC is not supported as fast clock source"))); +#endif + /* * Estimate number of openable files. This must happen after setting up * semaphores, because on some platforms semaphores count as open files. diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c index e54bf1e760f..e882220b9a0 100644 --- a/src/backend/tcop/postgres.c +++ b/src/backend/tcop/postgres.c @@ -4152,6 +4152,17 @@ PostgresSingleUserMain(int argc, char *argv[], */ CreateSharedMemoryAndSemaphores(); + /* + * Initialize high-precision interval timing. + * Raise FATAL error if RDTSC is requested but not available. + */ + INSTR_TIME_INITIALIZE(true); + +#if defined(__x86_64__) && defined(__linux__) + if (fast_clock_source == FAST_CLOCK_SOURCE_RDTSC && (!has_rdtsc || !has_rdtscp)) + ereport(FATAL, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("TSC is not supported as fast clock source"))); +#endif + /* * Estimate number of openable files. This must happen after setting up * semaphores, because on some platforms semaphores count as open files. diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c index c339c35b25d..3f401faf3de 100644 --- a/src/backend/utils/init/postinit.c +++ b/src/backend/utils/init/postinit.c @@ -809,9 +809,6 @@ InitPostgres(const char *in_dbname, Oid dboid, /* Initialize portal manager */ EnablePortalManager(); - /* initialize high-precision interval timing */ - INSTR_TIME_INITIALIZE(); - /* * Load relcache entries for the shared system catalogs. This must create * at least entries for pg_database and catalogs used for authentication. diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat index 7c60b125564..c68b3ff1184 100644 --- a/src/backend/utils/misc/guc_parameters.dat +++ b/src/backend/utils/misc/guc_parameters.dat @@ -1041,6 +1041,13 @@ max => '3', }, +{ name => 'fast_clock_source', type => 'enum', context => 'PGC_POSTMASTER', group => 'RESOURCES_TIME', + short_desc => 'Use of fast clock source.', + variable => 'fast_clock_source', + boot_val => 'FAST_CLOCK_SOURCE_TRY', + options => 'fast_clock_source_options', +}, + { name => 'file_copy_method', type => 'enum', context => 'PGC_USERSET', group => 'RESOURCES_DISK', short_desc => 'Selects the file copy method.', variable => 'file_copy_method', diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c index 73ff6ad0a32..3614aaf1876 100644 --- a/src/backend/utils/misc/guc_tables.c +++ b/src/backend/utils/misc/guc_tables.c @@ -90,6 +90,7 @@ #include "tcop/tcopprot.h" #include "tsearch/ts_cache.h" #include "utils/builtins.h" +#include "portability/instr_time.h" #include "utils/bytea.h" #include "utils/float.h" #include "utils/guc_hooks.h" @@ -371,6 +372,15 @@ static const struct config_enum_entry huge_pages_options[] = { {NULL, 0, false} }; +static const struct config_enum_entry fast_clock_source_options[] = { + {"try", FAST_CLOCK_SOURCE_TRY, false}, + {"off", FAST_CLOCK_SOURCE_OFF, false}, +#if defined(__x86_64__) && defined(__linux__) + {"rdtsc", FAST_CLOCK_SOURCE_RDTSC, false}, +#endif + {NULL, 0, false} +}; + static const struct config_enum_entry huge_pages_status_options[] = { {"off", HUGE_PAGES_OFF, false}, {"on", HUGE_PAGES_ON, false}, diff --git a/src/bin/pg_test_timing/pg_test_timing.c b/src/bin/pg_test_timing/pg_test_timing.c index 62e308dd965..3ffa95769a5 100644 --- a/src/bin/pg_test_timing/pg_test_timing.c +++ b/src/bin/pg_test_timing/pg_test_timing.c @@ -174,7 +174,7 @@ test_timing(unsigned int duration, bool fast_timing) char *time_source = NULL; bool fast_timing_available = false; - INSTR_TIME_INITIALIZE(); + INSTR_TIME_INITIALIZE(true); #if !defined(WIN32) && defined(__x86_64__) && defined(__linux__) if (fast_timing && has_rdtsc) diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c index 7b64fdaed34..78e5b40a7bb 100644 --- a/src/bin/pgbench/pgbench.c +++ b/src/bin/pgbench/pgbench.c @@ -7335,7 +7335,7 @@ main(int argc, char **argv) } /* initialize high-precision interval timing */ - INSTR_TIME_INITIALIZE(); + INSTR_TIME_INITIALIZE(false); /* opening connection... */ con = doConnect(); diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c index a0b3bafe20c..ec8748002d8 100644 --- a/src/bin/psql/startup.c +++ b/src/bin/psql/startup.c @@ -329,7 +329,7 @@ main(int argc, char *argv[]) PQsetNoticeProcessor(pset.db, NoticeProcessor, NULL); /* initialize high-precision interval timing */ - INSTR_TIME_INITIALIZE(); + INSTR_TIME_INITIALIZE(false); SyncVariables(); diff --git a/src/common/instr_time.c b/src/common/instr_time.c index fdf47699f20..02b57edfb9b 100644 --- a/src/common/instr_time.c +++ b/src/common/instr_time.c @@ -24,6 +24,17 @@ #include "portability/instr_time.h" +int fast_clock_source = FAST_CLOCK_SOURCE_TRY; + +void +pg_initialize_timing(bool try_fast) +{ +#if defined(__x86_64__) && defined(__linux__) + if (try_fast) + pg_initialize_rdtsc(); +#endif +} + #ifndef WIN32 /* * Stores what the number of cycles needs to be multiplied with to end up diff --git a/src/include/portability/instr_time.h b/src/include/portability/instr_time.h index 33e506f3526..22ee991d2c9 100644 --- a/src/include/portability/instr_time.h +++ b/src/include/portability/instr_time.h @@ -81,6 +81,14 @@ typedef struct instr_time #define NS_PER_MS INT64CONST(1000000) #define NS_PER_US INT64CONST(1000) +typedef enum +{ + FAST_CLOCK_SOURCE_TRY, + FAST_CLOCK_SOURCE_OFF, + FAST_CLOCK_SOURCE_RDTSC +} FastClockSourceType; + +extern int fast_clock_source; #ifndef WIN32 @@ -147,7 +155,7 @@ static inline instr_time pg_get_ticks_fast(void) { #if defined(__x86_64__) && defined(__linux__) - if (has_rdtsc) + if (likely(has_rdtsc && fast_clock_source != FAST_CLOCK_SOURCE_OFF)) { instr_time now; @@ -163,7 +171,7 @@ static inline instr_time pg_get_ticks(void) { #if defined(__x86_64__) && defined(__linux__) - if (has_rdtscp) + if (likely(has_rdtscp && fast_clock_source != FAST_CLOCK_SOURCE_OFF)) { instr_time now; uint32 unused; @@ -212,16 +220,11 @@ pg_ticks_to_ns(int64 ticks) return ns; } -static inline void -pg_initialize_get_ticks() -{ -#if defined(__x86_64__) && defined(__linux__) - pg_initialize_rdtsc(); -#endif -} +extern void +pg_initialize_timing(bool try_fast); -#define INSTR_TIME_INITIALIZE() \ - pg_initialize_get_ticks() +#define INSTR_TIME_INITIALIZE(try_fast) \ + pg_initialize_timing(try_fast) #define INSTR_TIME_SET_CURRENT_FAST(t) \ ((t) = pg_get_ticks_fast()) @@ -260,7 +263,7 @@ GetTimerFrequency(void) return (double) f.QuadPart; } -#define INSTR_TIME_INITIALIZE() +#define INSTR_TIME_INITIALIZE(try_fast) #define INSTR_TIME_SET_CURRENT_FAST(t) \ ((t) = pg_query_performance_counter()) diff --git a/src/include/utils/guc_tables.h b/src/include/utils/guc_tables.h index 71a80161961..63440b8e36c 100644 --- a/src/include/utils/guc_tables.h +++ b/src/include/utils/guc_tables.h @@ -60,6 +60,7 @@ enum config_group CONN_AUTH_TCP, CONN_AUTH_AUTH, CONN_AUTH_SSL, + RESOURCES_TIME, RESOURCES_MEM, RESOURCES_DISK, RESOURCES_KERNEL, -- 2.51.0