Re: Addition of --no-sync to pg_upgrade for test speedup

On Fri, Dec 17, 2021 at 09:47:05AM -0500, Bruce Momjian wrote:
> On Fri, Dec 17, 2021 at 10:21:04AM +0100, Peter Eisentraut wrote:
>> I think that is reasonable.

Thanks. I have applied that, as that really helped here.

>> Maybe we could have some global option, like some environment variable, that
>> enables the "sync" mode in all tests, so it's easy to test that once in a
>> while. Not really a requirement for your patch, but an idea in case this is
>> a concern.
>
> Yes, I think it would be good to see all the places we might want to
> pass the no-sync option.

The remaining places in src/bin/ that I can see are pg_resetwal, where
we would fsync() a WAL segment full of zeros, and pg_recvlogical
OutputFsync(), which does not point to much data, I guess. The first
one may be worth it, but that's just 16MB we are talking about and
WriteEmptyXLOG() is not a code path taken currently by the tests.

We could introduce a new environment variable if one wishes to enforce
those flushes, say PG_TEST_SYNC, on top of patching any TAP test that
has a --no-sync to filter it out.
--
Michael