Re: Possible performance regression in version 10.1 with pgbench read-write tests.

Andres Freund <andres@anarazel.de> writes:
> I'm a bit hesitant to just revert without further evaluation - it's just
> about as likely we'll regress on other hardware / kernel
> versions.

I looked into the archives for the discussion that led up to ecb0d20a9,
and found it here:

https://www.postgresql.org/message-id/flat/8536.1475704230%40sss.pgh.pa.us

The test cases I tried in that thread said that POSIX semas were *faster*
... by single-digit percentages, but still faster.  So I think we really
need to study this issue, rather than just take one contrary result as
being gospel.

            regards, tom lane