From: Andres Freund <andres@anarazel.de>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: aio: Combine io_uring memory mappings, if supported
Date: Tue, 08 Jul 2025 03:20:18 +0000
Message-ID: <E1uYysU-005Cab-1I@gemulon.postgresql.org> (raw)
aio: Combine io_uring memory mappings, if supported
By default io_uring creates a shared memory mapping for each io_uring
instance, leading to a large number of memory mappings. Unfortunately a large
number of memory mappings slows things down, backend exit is particularly
affected. To address that, newer kernels (6.5) support using user-provided
memory for the memory. By putting the relevant memory into shared memory we
don't need any additional mappings.
On a system with a new enough kernel and liburing, there is no discernible
overhead when doing a pgbench -S -C anymore.
Reported-by: MARK CALLAGHAN <mdcallag@gmail.com>
Reviewed-by: "Burd, Greg" <greg@burd.me>
Reviewed-by: Jim Nasby <jnasby@upgrade.com>
Discussion: https://postgr.es/m/CAFbpF8OA44_UG+RYJcWH9WjF7E3GA6gka3gvH6nsrSnEe9H0NA@mail.gmail.com
Backpatch-through: 18
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/f54af9f2679d5987b4680e742ac9bd585260e620
Modified Files
--------------
configure | 17 +++
configure.ac | 7 +
meson.build | 6 +
src/backend/storage/aio/method_io_uring.c | 210 +++++++++++++++++++++++++++++-
src/include/pg_config.h.in | 3 +
src/tools/pgindent/typedefs.list | 1 +
6 files changed, 238 insertions(+), 6 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: andres@anarazel.de, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: aio: Combine io_uring memory mappings, if supported
In-Reply-To: <E1uYysU-005Cab-1I@gemulon.postgresql.org>
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