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Replace random(), pg_erand48(), etc with a better PRNG API and algorithm.

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Standardize on xoroshiro128** as our basic PRNG algorithm, eliminating
a bunch of platform dependencies as well as fundamentally-obsolete PRNG
code.  In addition, this API replacement will ease replacing the
algorithm again in future, should that become necessary.

xoroshiro128** is a few percent slower than the drand48 family,
but it can produce full-width 64-bit random values not only 48-bit,
and it should be much more trustworthy.  It's likely to be noticeably
faster than the platform's random(), depending on which platform you
are thinking about; and we can have non-global state vectors easily,
unlike with random().  It is not cryptographically strong, but neither
are the functions it replaces.

Fabien Coelho, reviewed by Dean Rasheed, Aleksander Alekseev, and myself

Discussion: https://postgr.es/m/alpine.DEB.2.22.394.2105241211230.165418@pseudo
This commit is contained in:
Tom Lane
2021-11-28 21:32:36 -05:00
parent f44ceb46ec
commit 3804539e48
50 changed files with 543 additions and 480 deletions
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5
src/bin/pg_test_fsync/pg_test_fsync.c
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@ -15,6 +15,7 @@
#include "access/xlogdefs.h"
#include "common/logging.h"
#include "common/pg_prng.h"
#include "getopt_long.h"
/*
@ -117,6 +118,8 @@ main(int argc, char *argv[])
pqsignal(SIGHUP, signal_cleanup);
#endif
pg_prng_seed(&pg_global_prng_state, (uint64) time(NULL));
prepare_buf();
test_open();
@ -233,7 +236,7 @@ prepare_buf(void)
/* write random data into buffer */
for (ops = 0; ops < DEFAULT_XLOG_SEG_SIZE; ops++)
full_buf[ops] = random();
full_buf[ops] = (char) pg_prng_int32(&pg_global_prng_state);
buf = (char *) TYPEALIGN(XLOG_BLCKSZ, full_buf);
}