MIME-Version: 1.0
References: <aa8QlTVEDhG1JU0Z@nathan>
 <CAN55FZ08kqmA+B9pzPDy-QstxAd=cK-RqjbR3cWBjPF_8-FXAw@mail.gmail.com>
 <abBQbdFa6OsG8TGu@nathan>
 <CAN55FZ3jXs7XDsP_-v_jUBquRu4uAdheN3xcmW=WhAyKwFLSjg@mail.gmail.com>
 <abGv0ScUWVa6eogw@nathan>
 <CAN55FZ3gdK8dGrEo0M6KFW97OaF8TUbjO_dFoxQKi63davE-jA@mail.gmail.com>
 <abG8R6HkOHyUuyWb@nathan>
 <CAN55FZ0yfETy4UEA5rOJ9S06JSOtiWF8TW_+yi3yjVAcrLqKLA@mail.gmail.com>
 <abHTvkeIK37hj9oS@nathan>
 <CAN55FZ1sn-2tVX_n9C5UNBCfDPjSDOCT4zkMeDsB7MaZ9SUBTw@mail.gmail.com>
 <abL5ylYjmopRRmvy@nathan>
 <CAN55FZ0oYuVHZ=TdJofj0WA3mG77XumVsGJgG8gnav9kexr+wg@mail.gmail.com>
In-Reply-To: 
 <CAN55FZ0oYuVHZ=TdJofj0WA3mG77XumVsGJgG8gnav9kexr+wg@mail.gmail.com>
From: Nazir Bilal Yavuz <byavuz81@gmail.com>
Date: Fri, 13 Mar 2026 16:34:49 +0300
Message-ID: 
 <CAN55FZ0ocS6cBHEWqHv2s-dK91U6OdVLBqj7VexTehtBtioDbA@mail.gmail.com>
Subject: Re: Speed up COPY FROM text/CSV parsing using SIMD
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Manni Wood <manni.wood@enterprisedb.com>, KAZAR Ayoub <ma_kazar@esi.dz>,
	Neil Conway <neil.conway@gmail.com>, Andrew Dunstan <andrew@dunslane.net>,
	Shinya Kato <shinya11.kato@gmail.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Content-Type: text/plain; charset="UTF-8"
Archived-At: 
 <https://www.postgresql.org/message-id/CAN55FZ0ocS6cBHEWqHv2s-dK91U6OdVLBqj7VexTehtBtioDbA%40mail.gmail.com>
Precedence: bulk

Hi,

On Fri, 13 Mar 2026 at 14:57, Nazir Bilal Yavuz <byavuz81@gmail.com> wrote:
>
> Unfortunately, v15 causes a regression for a 'csv & wide & 1/3' case
> on my end. v14 was taking 8000ms but v15 took ~9100ms. If we add the
> tmp_hit_eof variable then the regression disappears. Also, if I use a
> struct like below, regression disappears again.

> When I removed the tmp_hit_eof variable on v14, I didn't encounter any
> regression. I really don't understand why this is happening on my end.
> Manni didn't encounter any regression on the benchmark [1].

Problem might be related to gcc. I am using Debian Trixie and my
current gcc version is 'gcc version 14.2.0 (Debian 14.2.0-19)'. If I
compile Postgres with 'Debian clang version 19.1.7 (3+b1)', then there
is no regression, which makes more sense IMO.

Here is a comparison for csv & wide & 1/3 case. Postgres is compiled
with buildtype=debugoptimized and default_toast_compression is lz4.

+--------------------------------+
|   CSV & WIDE & 1/3, LZ4, -O2   |
+--------------+--------+--------+
|              |   gcc  |  clang |
|              | 14.0.2 | 19.1.7 |
+--------------+--------+--------+
|  old master  |  8250  |  10400 |
+--------------+--------+--------+
|      v14     |  8100  |  9800  |
+--------------+--------+--------+
|      v15     |  9200  |  9800  |
+--------------+--------+--------+
| v15 + struct |  7750  |  9800  |
+--------------+--------+--------+

-- 
Regards,
Nazir Bilal Yavuz
Microsoft