Export zend_accel_shared_globals

[realFlowControl]

Hey folks 👋

I could not find any other way to access this information from an extension:

php-src/ext/opcache/ZendAccelerator.h

Lines 244 to 284 in 35fbb00

	typedef struct _zend_accel_shared_globals {
	/* Cache Data Structures */
	zend_ulong hits;
	zend_ulong misses;
	zend_ulong blacklist_misses;
	zend_ulong oom_restarts; /* number of restarts because of out of memory */
	zend_ulong hash_restarts; /* number of restarts because of hash overflow */
	zend_ulong manual_restarts; /* number of restarts scheduled by opcache_reset() */
	zend_accel_hash hash; /* hash table for cached scripts */
	size_t map_ptr_last;
	/* Directives & Maintenance */
	time_t start_time;
	time_t last_restart_time;
	time_t force_restart_time;
	bool accelerator_enabled;
	bool restart_pending;
	zend_accel_restart_reason restart_reason;
	bool cache_status_before_restart;
	#ifdef ZEND_WIN32
	LONGLONG mem_usage;
	LONGLONG restart_in;
	#endif
	bool restart_in_progress;
	bool jit_counters_stopped;
	/* Preloading */
	zend_persistent_script *preload_script;
	zend_persistent_script **saved_scripts;
	/* uninitialized HashTable Support */
	uint32_t uninitialized_bucket[-HT_MIN_MASK];
	/* Tracing JIT */
	void *jit_traces;
	const void **jit_exit_groups;
	/* Interned Strings Support (must be the last element) */
	ZEND_SET_ALIGNED(ZEND_STRING_TABLE_POS_ALIGNMENT, zend_string_table interned_strings);
	} zend_accel_shared_globals;

There is a user land function opcache_get_status() but this does way more, especially unnecessary things when not using the data in PHP, but in another C/Rust extension.

I'd like to add a bit more observability to the OPcache. IIRC @arnaud-lb is working on OPcache, is that right?

[cmb69]

Did you try (zend_accel_shared_globals *) ZSMMG(app_shared_globals)?

[bwoebi]

@cmb69 ZSMMG() isn't shared either. But yes, it would make more sense to expose that one instead.

[bwoebi]

@realFlowControl Any reason you create an extra function instead of just exporting the global?

[cmb69]

Hmm,

php-src/ext/opcache/ZendAccelerator.h

Line 295 in 6a51062

extern zend_accel_shared_globals *accel_shared_globals;

[realFlowControl]

That is because it is declared here, but defined somewhere else. The definition is here:

php-src/ext/opcache/ZendAccelerator.c

Line 112 in 6a51062

zend_accel_shared_globals *accel_shared_globals = NULL;

[cmb69]

That is because it is declared here, but defined somewhere else. The definition is here:

Wouldn't ZEND_EXT_API extern zend_accel_shared_globals *accel_shared_globals; do?

[realFlowControl]

Jup, thanks @bwoebi and @cmb69. I updated the PR.

    zend_smm_shared_globals **smm_shared_globals;
    smm_shared_globals = dlsym(opcache_handle, "smm_shared_globals");
    zend_accel_shared_globals * accel_shared_globals = (zend_accel_shared_globals *)(*smm_shared_globals)->app_shared_globals;
    if (accel_shared_globals)
        printf("restart pending: %d\n", accel_shared_globals->restart_pending);

Is working and gets me the data I need 😄

Update: looks like Windows want's the ZEND_EXT_API in the zend_shared_alloc.h as well

[arnaud-lb]

Looks good to me, but could we possibly expose more information via opcache_get_status() instead?

[realFlowControl]

Hey @arnaud-lb,
we could expose more via opcache_get_status() as well, in my use case I see two problems:

• I need that data in an extension, this function prepares data for user land, which just adds overhead not needed in this case
• calling this function from outside a request phase is doable, but tricky

Actually I'd like to add an observer API to the opcache so that you are able to observe certain events when they happen, but I won't be able to in time for 8.4.
Would you be interested to talk about and target something for 8.5/9.0?
In the mean time, this would help a lot for extensions that need to collect some internal opcache data.

[dstogov]

I'm against this change. This is not an universal solution.
It won't work on Windows, except you link your observer with opcache, but then it won't wok without opcache.

[bwoebi]

@dstogov Why won't it work on Windows to use DL_FETCH_SYMBOL() there?

[dstogov]

@dstogov Why won't it work on Windows to use DL_FETCH_SYMBOL() there?

I didn't try DL_FETCH_SYMBOL().
Transparent linking of public symbols between different DSO definitely doesn't work as on Linux.

[bwoebi]

@dstogov We've definitely been successfully using DL_FETCH_SYMBOL on windows with the other ZEND_EXT_API symbols opcache exports (jit functions).

So at least under that aspect it would be an universal solution.

[dstogov]

OK. I don't care.