From: Pierre C <lists@peufeu.com>
To: Josh Berkus <josh@agliodbs.com>
To: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: PostgreSQL as a local in-memory cache
Date: Thu, 17 Jun 2010 20:44:04 +0200
Message-ID: <op.vegjnqfreorkce@apollo13> (raw)
In-Reply-To: <4C1A5B81.8050908@agliodbs.com>
References: <cb0fb58c-9134-4314-a1d0-08fc39f911a6@40g2000pry.googlegroups.com>
<18287446-8677-46d6-a581-c4777f60ebda@40g2000pry.googlegroups.com>
<4C1A5B81.8050908@agliodbs.com>
> Especially as, in repeated tests, PostgreSQL with persistence turned off
> is just as fast as the fastest nondurable NoSQL database. And it has a
> LOT more features.
An option to completely disable WAL for such use cases would make it a lot
faster, especially in the case of heavy concurrent writes.
> Now, while fsync=off and tmpfs for WAL more-or-less eliminate the IO for
> durability, they don't eliminate the CPU time.
Actually the WAL overhead is some CPU and lots of locking.
> Which means that a caching version of PostgreSQL could be even faster.
> To do that, we'd need to:
>
> a) Eliminate WAL logging entirely
> b) Eliminate checkpointing
> c) Turn off the background writer
> d) Have PostgreSQL refuse to restart after a crash and instead call an
> exteral script (for reprovisioning)
>
> Of the three above, (a) is the most difficult codewise.
Actually, it's pretty easy, look in xlog.c
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: lists@peufeu.com, josh@agliodbs.com
Subject: Re: PostgreSQL as a local in-memory cache
In-Reply-To: <op.vegjnqfreorkce@apollo13>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox