From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Greg Stark <stark(at)mit(dot)edu>, Peter Geoghegan <pg(at)heroku(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Misaligned BufferDescriptors causing major performance problems on AMD |
Date: | 2014-02-05 16:37:37 |
Message-ID: | 20140205163737.GE28649@alap3.anarazel.de |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On 2014-02-05 11:23:29 -0500, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > And I think somebody already thought about it (c.f. ALIGNOF_BUFFER), it
> > just wasn't updated in the last 10 years.
>
> No, ALIGNOF_BUFFER is there because we read something that said that I/O
> transfers between userspace and kernel disk cache would be faster with
> aligned buffers. There's been no particular thought given to alignment
> of other data structures, AFAIR.
But it's not aligned anymore on at last half a decade's hardware, and
it's what we already align *all* bigger ShmemAlloc() values with. And
BufferDescriptors surely counts as larger in its entirety.
> It may well be that your proposal is spot on. But I'd like to see some
> data-structure-by-data-structure measurements, rather than assuming that
> alignment must be a good thing.
I am fine with just aligning BufferDescriptors properly. That has
clearly shown massive improvements.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2014-02-05 16:40:49 | Re: jsonb and nested hstore |
Previous Message | Merlin Moncure | 2014-02-05 16:33:25 | Re: jsonb and nested hstore |