Allow retrieving x86 TSC frequency/flags from CPUID
This adds additional x86 specific CPUID checks for flags needed for
determining whether the Time-Stamp Counter (TSC) is usable on a given system,
as well as a helper function to retrieve the TSC frequency from CPUID.
This is intended for a future patch that will utilize the TSC to lower the
overhead of timing instrumentation.
In passing, always make pg_cpuid_subleaf reset the variables used for its
result, to avoid accidentally using stale results if __get_cpuid_count errors
out and the caller doesn't check for it.
Author: Lukas Fittl <lukas@fittl.com>
Author: David Geier <geidav.pg@gmail.com>
Author: Andres Freund <andres@anarazel.de>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: David Geier <geidav.pg@gmail.com>
Reviewed-by: John Naylor <john.naylor@postgresql.org>
Reviewed-by: Jakub Wartak <jakub.wartak@enterprisedb.com> (in an earlier version)
Discussion: https://www.postgresql.org/message-id/flat/20200612232810.f46nbqkdhbutzqdg%40alap3.anarazel.de
Branch
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master
Details
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https://git.postgresql.org/pg/commitdiff/bcb2cf41f964e9ed4d27abe4dee8daa249f659bb
Modified Files
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src/include/port/pg_cpu.h | 12 +++-
src/port/pg_cpu_x86.c | 138 ++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 145 insertions(+), 5 deletions(-)
