Re: logical decoding : exceeded maxAllocatedDescs for .spill files

On Thu, Jan 09, 2020 at 12:45:41AM -0500, Tom Lane wrote:
> Noah Misch <noah(at)leadboat(dot)com> writes:
> > Even so, a web search for "extend_brk" led to the answer. By default, 32-bit
> > AIX binaries get only 256M of RAM for stack and sbrk. The new regression test
> > used more than that, hence this crash.
>
> Hm, so
>
> (1) Why did we get a crash and not some more-decipherable out-of-resources
> error? Can we improve that experience?

By default, 32-bit AIX binaries have maxdata:0x00000000. Specifying
maxdata:0x10000000 provides the same 256M of RAM, yet it magically changes the
SIGSEGV to ENOMEM:

$ OBJECT_MODE=32 gcc maxdata.c && ./a.out
Segmentation fault
$ OBJECT_MODE=32 gcc -Wl,-bmaxdata:0x00000000 maxdata.c && ./a.out
Segmentation fault
$ OBJECT_MODE=32 gcc -Wl,-bmaxdata:0x10000000 maxdata.c && ./a.out
done at 255 MiB: Not enough space

We could add -Wl,-bmaxdata:0x10000000 (or a higher value) to LDFLAGS when
building for 32-bit AIX.

> (2) Should we be dialing back the resource consumption of this test?
> Even on machines where it doesn't fail outright, I'd imagine that it's
> costing a lot of buildfarm cycles. Is it actually worth that?

The test's resource usage, being quite low, should not be a factor in the
test's fate. On my usual development machine, the entire
006_logical_decoding.pl file takes just 3s and ~250 MiB of RAM.