boost/interprocess
2
0
Fork 0
mirror of https://github.com/boostorg/interprocess.git synced 2026-01-19 04:12:13 +00:00
Code Issues Projects Releases Wiki Activity

Rework documentation for systems that do not fully support process-shared features

Browse Source
This commit is contained in:
Ion Gaztañaga
2026-01-02 11:58:03 +01:00
parent e006a65aac
commit 37e334e80c
1 changed files with 17 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

34
doc/interprocess.qbk
View File

@@ -6730,9 +6730,9 @@ Please take in care that, for XSI synchronization primitives (e.g. `xsi_shared_m
[endsect]
[section:notes_linux Notes for Linux users]
[section:notes_unix Notes for Unix users]
[section:notes_linux_shm_folder Shared memory emulation folder]
[section:notes_unix_shm_folder Shared memory emulation folder]
On systems without POSIX shared memory support, shared memory objects are implemented as memory mapped files, using a directory
placed in "/tmp" that can include (if `BOOST_INTERPROCESS_HAS_KERNEL_BOOTTIME` is defined) the last bootup time (if the OS supports it).
@@ -6753,6 +6753,10 @@ to determine the shared directory at runtime, define `BOOST_INTERPROCESS_SHARED_
[endsect]
[endsect]
[section:notes_linux Notes for Linux users]
[section:notes_linux_overcommit Overcommit]
The committed address space is the total amount of virtual memory (swap or physical memory/RAM) that the kernel might have to supply
@@ -6774,25 +6778,15 @@ change this overcommit behaviour.
[endsect]
[section:notes_freebsd Notes for FreeBSD users]
[section:notes_macos_bsd Notes for MacOS and BSD users]
[section:notes_freebsd_umtx_vnode_persistent Process-shared synchronization primitives and ['kern.ipc.umtx_vnode_persistent]]
Starting from FreeBSD 11, declares the macro _POSIX_THREAD_PROCESS_SHARED. However, the default behavior is different from the one on Linux.
If you want to use this feature, according to the man page of libthr(3), you should check sysctl's ['kern.ipc.umtx_vnode_persistent]:
* ['kern.ipc.umtx_vnode_persistent]: By default, a shared lock backed by a mapped file in memory is automatically destroyed on the last
unmap of the corresponding file's page, which is allowed by POSIX. Setting the sysctl to 1 makes such a shared lock object persist until
the vnode is recycled by the Virtual File System. Note that in case file is not opened and not mapped, the kernel might recycle it at
any moment, making this sysctl less useful than it sounds.
If you want mapped files to remain useful after the last handle is closed, set this variable to 1.
Support for _POSIX_THREAD_PROCESS_SHARED is inexistent (OpenBSD/NetBSD, old FreeBSD) or incomplete/buggy (FreeBSD>=11, MacOS).
Process-shared synchronization primitives are emulated with atomics, which have suboptimal performance and are unrecoverable
under process crashes while holding the lock.
[endsect]
[endsect]
[section:notes_freebsd Notes for MacOs users]
[section:notes_macos Notes for MacOs users]
[section:notes_macos_sandboxed Limitations for sandboxed applications]
@@ -6808,6 +6802,12 @@ Please see Apple documentation
[endsect]
[section:notes_other_xsi Notes for QNX, Android, Haiku, VxWorks and Emscriptem users]
Those operating system don't offer support XSI IPC mechanisms, so associated utilities are not available.
[endsect]
[endsect]
[section:thanks_to Thanks to...]