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aio: Combine io_uring memory mappings, if supported

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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
This commit is contained in:
Andres Freund
2025-07-07 21:03:16 -04:00
parent 55a780e947
commit f54af9f267
6 changed files with 238 additions and 6 deletions
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7
configure.ac
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@ -1420,6 +1420,13 @@ if test "$with_libxslt" = yes ; then
AC_CHECK_LIB(xslt, xsltCleanupGlobals, [], [AC_MSG_ERROR([library 'xslt' is required for XSLT support])])
fi
if test "$with_liburing" = yes; then
_LIBS="$LIBS"
LIBS="$LIBURING_LIBS $LIBS"
AC_CHECK_FUNCS([io_uring_queue_init_mem])
LIBS="$_LIBS"
fi
if test "$with_lz4" = yes ; then
AC_CHECK_LIB(lz4, LZ4_compress_default, [], [AC_MSG_ERROR([library 'lz4' is required for LZ4 support])])
fi