public inbox for [email protected]  

help / color / mirror / Atom feed

From: Andres Freund <[email protected]>
To: Thomas Munro <[email protected]>
Cc: pgsql-hackers <[email protected]>
Subject: Re: A qsort template
Date: Wed, 17 Feb 2021 22:02:22 -0800
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+hUKGJ2-eaDqAum5bxhpMNhvuJmRDZxB_Tow0n-gse+HG0Yig@mail.gmail.com>
References: <CA+hUKGJ2-eaDqAum5bxhpMNhvuJmRDZxB_Tow0n-gse+HG0Yig@mail.gmail.com>

Hi,

On 2021-02-18 16:09:49 +1300, Thomas Munro wrote:
> In another thread[1], I proposed $SUBJECT, but then we found a better
> solution to that thread's specific problem.  The general idea is still
> good though: it's possible to (1) replace several existing copies of
> our qsort algorithm with one, and (2) make new specialised versions a
> bit more easily than the existing Perl generator allows.  So, I'm back
> with a rebased stack of patches.  I'll leave specific cases for new
> worthwhile specialisations for separate proposals; I've heard about
> several.

One place that could benefit is the qsort that BufferSync() does at the
start. I tried your patch for that, and it does reduce the sort time
considerably. For 64GB of mostly dirty shared_buffers from ~1.4s to
0.6s.

Now, obviously one can argue that that's not going to be the crucial
spot, and wouldn't be entirely wrong. OTOH, in my AIO branch I see
checkpointer doing ~10GB/s, leading to the sort being a measurable
portion of the overall time.

Greetings,

Andres Freund

view thread (52+ messages)  latest in thread

reply

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: [email protected]
  Cc: [email protected], [email protected]
  Subject: Re: A qsort template
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox