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From: Bruce Momjian <bruce@momjian.us>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Luca Ferrari <fluca1978@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: FreeBSD UFS & fsync
Date: Fri, 12 Mar 2021 14:39:58 -0500
Message-ID: <20210312193958.GA5362@momjian.us> (raw)
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On Fri, Mar 12, 2021 at 10:33:29PM +1300, Thomas Munro wrote:
> On Fri, Mar 12, 2021 at 10:09 PM Luca Ferrari <fluca1978@gmail.com> wrote:
> >        fdatasync                         16269.365 ops/sec      61 usecs/op
> >        fsync                              8471.429 ops/sec     118 usecs/op
> 
> > Non-sync'ed 8kB writes:
> >        write                            278484.510 ops/sec       4 usecs/op
> 
> > tps = 136.963971 (excluding connections establishing)
> 
> It looks like your system is performing very badly for some other
> reason, so that synchronous I/O waits are only a small proportion of
> the time, and thus fsync=off doesn't speed things up very much.  I'd
> look into profiling the system to try to figure out what it's doing...
> maybe it's suffering from super slow hypercalls for gettimeofday(), or
> something like that?

And we have pg_test_timing for gettimeofday() testing.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  The usefulness of a cup is in its emptiness, Bruce Lee






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