Disable opcache if no SHM backend is available #19350
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| zps_startup_failure("No available SHM backend", NULL, accelerator_remove_cb); | ||
| /* Do not abort PHP startup */ | ||
| return SUCCESS; | ||
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Nit: Whitespace that isn't consistent with rest of switch cases. :)
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I didn't get. You compile opcache into PHP just to say it can't work on this platform...
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@dstogov This comes after https://wiki.php.net/rfc/make_opcache_required. The aim is to consistently provide opcache without having to install it separately, and without having to load the extension, but keep PHP compatible with rare systems that don't support any of Opcache's backends.
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So, for these systems we provide a feature that can't work and just waste resources.
Note that compilation of opcache for these systems may be a problem as well.
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In theory we could at least make the file cache work, at least when opcache.file_cache is specified. In the long term, always building opcache will help reduce complexity and some inconsistencies, even if it ends up being disabled as in this PR, or by opcache.enable(_cli)=0.
I've measured the overhead of building opcache: It is about 110KiB of .text in a -Os build. The total size of the .text section in a minimal PHP build is about 6MiB.
Note that compilation of opcache for these systems may be a problem as well.
I'm happy making changes to address these problems.
Currently,
./configurefails when no SHM backend is available (we support a wide range of systems with mmap(MAP_ANONYMOUS), shmget(), shm_open(), but some non-standard systems may not have any of these). Additionally, even after bypassing the configure check, Opcache emits a fatal error if no SHM backend is available.Changes in this PR:
cc @krakjoe @derickr