From f6e849fd7ce2a8954022bd23b94703975b3db0d1 Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Tue, 8 Oct 2024 15:45:26 -0300 Subject: [PATCH] linux: Add MAP_DROPPABLE from Linux 6.11 This request the page to be never written out to swap, it will be zeroed under memory pressure (so kernel can just drop the page), it is inherited by fork, it is not counted against @code{mlock} budget, and if there is no enough memory to service a page faults there is no fatal error (so not signal is sent). Tested with build-many-glibcs.py. Reviewed-by: H.J. Lu --- manual/llio.texi | 9 +++++++++ sysdeps/unix/sysv/linux/bits/mman-linux.h | 1 + sysdeps/unix/sysv/linux/tst-mman-consts.py | 2 +- 3 files changed, 11 insertions(+), 1 deletion(-) diff --git a/manual/llio.texi b/manual/llio.texi index a035c3e20f..05ab44c6e7 100644 --- a/manual/llio.texi +++ b/manual/llio.texi @@ -1762,6 +1762,15 @@ write dirty metadata out whenever dirty data is written out. Unlike most other flags, this one will fail unless @code{MAP_SHARED_VALIDATE} is also given. +@item MAP_DROPPABLE +Request the page to be never written out to swap, it will be zeroed +under memory pressure (so kernel can just drop the page), it is inherited +by fork, it is not counted against @code{mlock} budget, and if there is +not enough memory to service a page fault there is no fatal error (so no +signal is sent). + +The @code{MAP_DROPPABLE} flag is specific to Linux. + @end vtable @code{mmap} returns the address of the new mapping, or diff --git a/sysdeps/unix/sysv/linux/bits/mman-linux.h b/sysdeps/unix/sysv/linux/bits/mman-linux.h index 522333c50a..161a885096 100644 --- a/sysdeps/unix/sysv/linux/bits/mman-linux.h +++ b/sysdeps/unix/sysv/linux/bits/mman-linux.h @@ -43,6 +43,7 @@ #define MAP_PRIVATE 0x02 /* Changes are private. */ #define MAP_SHARED_VALIDATE 0x03 /* Share changes and validate extension flags. */ +#define MAP_DROPPABLE 0x08 /* Zero memory under memory pressure. */ #define MAP_TYPE 0x0f /* Mask for type of mapping. */ /* Other flags. */ diff --git a/sysdeps/unix/sysv/linux/tst-mman-consts.py b/sysdeps/unix/sysv/linux/tst-mman-consts.py index a1137eb1d5..2191bea36f 100644 --- a/sysdeps/unix/sysv/linux/tst-mman-consts.py +++ b/sysdeps/unix/sysv/linux/tst-mman-consts.py @@ -33,7 +33,7 @@ def main(): help='C compiler (including options) to use') args = parser.parse_args() linux_version_headers = glibcsyscalls.linux_kernel_version(args.cc) - linux_version_glibc = (6, 10) + linux_version_glibc = (6, 11) sys.exit(glibcextract.compare_macro_consts( '#define _GNU_SOURCE 1\n' '#include \n',