| #
e67565f5 |
| 20-Jun-2022 |
Max Kellermann |
Zend, ext/opcache: use PR_SET_VMA_ANON_NAME (Linux 5.17) (#8234)
The new Linux 5.17 feature PR_SET_VMA_ANON_NAME can give names to
anonymous private memory, see:
https://lwn.ne
Zend, ext/opcache: use PR_SET_VMA_ANON_NAME (Linux 5.17) (#8234)
The new Linux 5.17 feature PR_SET_VMA_ANON_NAME can give names to
anonymous private memory, see:
https://lwn.net/Articles/867818/
It can be useful while debugging, to identify which portion of the
process's memory belongs to which subsystem.
This is how /proc/PID/maps can look like:
555ccd400000-555ccdc00000 r-xp 00000000 00:00 0 [anon:huge_code_pages]
7f6ec6600000-7f6ec6800000 rw-p 00000000 00:00 0 [anon:zend_alloc]
The first mapping is the PHP executable copied to anonymous memory by
option "opcache.huge_code_pages". The second one is a memory area for
the "zend_alloc.h" memory allocator library.
Unfortunately, it is not possible to give names to shared memory
(MAP_SHARED), because Linux MAP_SHARED really maps /dev/zero (see
shmem_zero_setup()), which makes madvise_vma_anon_name() believe this
is a file mapping, failing the prctl() with EBADF.
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