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Make pgbench use erand48() rather than random().

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glibc renders random() thread-safe by wrapping a futex lock around it;
testing reveals that this limits the performance of pgbench on machines
with many CPU cores.  Rather than switching to random_r(), which is
only available on GNU systems and crashes unless you use undocumented
alchemy to initialize the random state properly, switch to our built-in
implementation of erand48(), which is both thread-safe and concurrent.

Since the list of reasons not to use the operating system's erand48()
is getting rather long, rename ours to pg_erand48() (and similarly
for our implementations of lrand48() and srand48()) and just always
use those.  We were already doing this on Cygwin anyway, and the
glibc implementation is not quite thread-safe, so pgbench wouldn't
be able to use that either.

Per discussion with Tom Lane.
This commit is contained in:
Robert Haas
2011-08-03 16:26:40 -04:00
parent ac36e6f71f
commit 4af43ee3f1
12 changed files with 40 additions and 62 deletions
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9
src/include/port.h
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@@ -380,12 +380,9 @@ extern off_t ftello(FILE *stream);
#endif
#endif
#ifndef HAVE_ERAND48
/* we assume all of these are present or missing together */
extern double erand48(unsigned short xseed[3]);
extern long lrand48(void);
extern void srand48(long seed);
#endif
extern double pg_erand48(unsigned short xseed[3]);
extern long pg_lrand48(void);
extern void pg_srand48(long seed);
#ifndef HAVE_FSEEKO
#define fseeko(a, b, c) fseek(a, b, c)