| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com> |
| Cc: | Magnus Hagander <magnus(at)hagander(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Greg Stark <stark(at)mit(dot)edu>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] log_destination=file |
| Date: | 2017-11-14 15:33:53 |
| Message-ID: | CA+TgmoYo00i+4f6gwAi8pcQ8hCkKr0J_7ZeZRTJJVJ2RK7uf1w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sun, Sep 10, 2017 at 5:29 AM, Dmitry Dolgov <9erthalion6(at)gmail(dot)com> wrote:
> average latency:
>
> clients patch master
> 10 0.321 0.286
> 20 0.669 0.602
> 30 1.016 0.942
> 40 1.358 1.280
> 50 1.727 1.637
That's still a noticeable slowdown, though. And we've had previous
reports of the overhead of logging being significant as well:
http://postgr.es/m/CACLsApsA7U0GCFpojVQem6SGTEkv8vnwdBfhVi+dqO+gu5gdCA@mail.gmail.com
I seem to recall a discussion, perhaps in-person, around the time Theo
submitted that patch where it was reported that the logging collector
could not be used on some systems he was working with because it
became a major performance bottleneck. With each backend writing its
own messages to a file, it was tolerable, but when you tried to funnel
everything through a single process, the back-pressure slowed down the
entire system unacceptably.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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