Re: multi-threaded pgbench

On Tue, 2009-07-28 at 23:38 -0400, Josh Williams wrote:
> Huh, running the patched version on a single thread with 128 clients
> just got it to crash.  Actually consistently, three times now.  Will try
> the same thing on the development box tomorrow morning to get some
> better debugging information.

So yeah, buffer overrun.

In pgbench.c FD_SETSIZE is redefined to get around the Windows default
of 64.  But this is done after bringing in winsock2.h (a couple levels
in as a result of first including postgres_fe.h).  So any fd_set is
built with an array of 64 descriptors, while pgbench thinks it has 1024
available to work with.

This was introduced a while back; the multi-threaded patch just makes it
visible by giving it an important pointer to write over.  Previously it
would just run over into the loop counter (and probably a couple other
things) and thus it'd continue on happily with the [sub]set it has.

In either case this seems to be a simple fix, to move that #define
earlier (see pgbench_win32.patch.)

- Josh Williams