Re: FreeBSD UFS & fsync

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Cc: Luca Ferrari <fluca1978(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: FreeBSD UFS & fsync
Date: 2021-03-12 19:39:58
Message-ID: 20210312193958.GA5362@momjian.us
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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(at)gmail(dot)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(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

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

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