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

On 2018-Jul-19, Amit Kapila wrote:

> On Thu, Feb 22, 2018 at 7:55 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> > On Wed, Feb 21, 2018 at 10:03 PM, Mithun Cy <mithun.cy@enterprisedb.com> wrote:
> >> seeing futex in the call stack andres suggested that following commit could
> >> be the reason for regression
> >>
> >> commit ecb0d20a9d2e09b7112d3b192047f711f9ff7e59
> >> Author: Tom Lane <tgl@sss.pgh.pa.us>
> >> Date:   2016-10-09 18:03:45 -0400
> >>
> >>     Use unnamed POSIX semaphores, if available, on Linux and FreeBSD.

> > Hmm.  So that commit might not have been the greatest idea.
> 
> It appears so.  I think we should do something about it as the
> regression is quite noticeable.

So the fix is just to revert the change for the linux makefile?  Sounds
easy enough, code-wise.  Do we need more evidence that it's harmful?

Since it was changed in pg10 not 11, I don't think this is an open-item
per se.  (Maybe an "older bug", if we must really have it there.)

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services