jemalloc/internal/prof.h

/******************************************************************************/
#ifdef JEMALLOC_H_TYPES

typedef struct prof_bt_s prof_bt_t;
typedef struct prof_cnt_s prof_cnt_t;
typedef struct prof_thr_cnt_s prof_thr_cnt_t;
typedef struct prof_ctx_s prof_ctx_t;
typedef struct prof_tdata_s prof_tdata_t;

/* Option defaults. */
#define	PROF_PREFIX_DEFAULT		"jeprof"
#define	LG_PROF_SAMPLE_DEFAULT		19
#define	LG_PROF_INTERVAL_DEFAULT	-1

/*
 * Hard limit on stack backtrace depth.  The version of prof_backtrace() that
 * is based on __builtin_return_address() necessarily has a hard-coded number
 * of backtrace frame handlers, and should be kept in sync with this setting.
 */
#define	PROF_BT_MAX			128

/* Maximum number of backtraces to store in each per thread LRU cache. */
#define	PROF_TCMAX			1024

/* Initial hash table size. */
#define	PROF_CKH_MINITEMS		64

/* Size of memory buffer to use when writing dump files. */
#define	PROF_DUMP_BUFSIZE		65536

/* Size of stack-allocated buffer used by prof_printf(). */
#define	PROF_PRINTF_BUFSIZE		128

/*
 * Number of mutexes shared among all ctx's.  No space is allocated for these
 * unless profiling is enabled, so it's okay to over-provision.
 */
#define	PROF_NCTX_LOCKS			1024

/*
 * prof_tdata pointers close to NULL are used to encode state information that
 * is used for cleaning up during thread shutdown.
 */
#define	PROF_TDATA_STATE_REINCARNATED	((prof_tdata_t *)(uintptr_t)1)
#define	PROF_TDATA_STATE_PURGATORY	((prof_tdata_t *)(uintptr_t)2)
#define	PROF_TDATA_STATE_MAX		PROF_TDATA_STATE_PURGATORY

#endif /* JEMALLOC_H_TYPES */
/******************************************************************************/
#ifdef JEMALLOC_H_STRUCTS

struct prof_bt_s {
	/* Backtrace, stored as len program counters. */
	void		**vec;
	unsigned	len;
};

#ifdef JEMALLOC_PROF_LIBGCC
/* Data structure passed to libgcc _Unwind_Backtrace() callback functions. */
typedef struct {
	prof_bt_t	*bt;
	unsigned	nignore;
	unsigned	max;
} prof_unwind_data_t;
#endif

struct prof_cnt_s {
	/*
	 * Profiling counters.  An allocation/deallocation pair can operate on
	 * different prof_thr_cnt_t objects that are linked into the same
	 * prof_ctx_t cnts_ql, so it is possible for the cur* counters to go
	 * negative.  In principle it is possible for the *bytes counters to
	 * overflow/underflow, but a general solution would require something
	 * like 128-bit counters; this implementation doesn't bother to solve
	 * that problem.
	 */
	int64_t		curobjs;
	int64_t		curbytes;
	uint64_t	accumobjs;
	uint64_t	accumbytes;
};

struct prof_thr_cnt_s {
	/* Linkage into prof_ctx_t's cnts_ql. */
	ql_elm(prof_thr_cnt_t)	cnts_link;

	/* Linkage into thread's LRU. */
	ql_elm(prof_thr_cnt_t)	lru_link;

	/*
	 * Associated context.  If a thread frees an object that it did not
	 * allocate, it is possible that the context is not cached in the
	 * thread's hash table, in which case it must be able to look up the
	 * context, insert a new prof_thr_cnt_t into the thread's hash table,
	 * and link it into the prof_ctx_t's cnts_ql.
	 */
	prof_ctx_t		*ctx;

	/*
	 * Threads use memory barriers to update the counters.  Since there is
	 * only ever one writer, the only challenge is for the reader to get a
	 * consistent read of the counters.
	 *
	 * The writer uses this series of operations:
	 *
	 * 1) Increment epoch to an odd number.
	 * 2) Update counters.
	 * 3) Increment epoch to an even number.
	 *
	 * The reader must assure 1) that the epoch is even while it reads the
	 * counters, and 2) that the epoch doesn't change between the time it
	 * starts and finishes reading the counters.
	 */
	unsigned		epoch;

	/* Profiling counters. */
	prof_cnt_t		cnts;
};

struct prof_ctx_s {
	/* Associated backtrace. */
	prof_bt_t		*bt;

	/* Protects nlimbo, cnt_merged, and cnts_ql. */
	malloc_mutex_t		*lock;

	/*
	 * Number of threads that currently cause this ctx to be in a state of
	 * limbo due to one of:
	 *   - Initializing per thread counters associated with this ctx.
	 *   - Preparing to destroy this ctx.
	 * nlimbo must be 1 (single destroyer) in order to safely destroy the
	 * ctx.
	 */
	unsigned		nlimbo;

	/* Temporary storage for summation during dump. */
	prof_cnt_t		cnt_summed;

	/* When threads exit, they merge their stats into cnt_merged. */
	prof_cnt_t		cnt_merged;

	/*
	 * List of profile counters, one for each thread that has allocated in
	 * this context.
	 */
	ql_head(prof_thr_cnt_t)	cnts_ql;
};

struct prof_tdata_s {
	/*
	 * Hash of (prof_bt_t *)-->(prof_thr_cnt_t *).  Each thread keeps a
	 * cache of backtraces, with associated thread-specific prof_thr_cnt_t
	 * objects.  Other threads may read the prof_thr_cnt_t contents, but no
	 * others will ever write them.
	 *
	 * Upon thread exit, the thread must merge all the prof_thr_cnt_t
	 * counter data into the associated prof_ctx_t objects, and unlink/free
	 * the prof_thr_cnt_t objects.
	 */
	ckh_t			bt2cnt;

	/* LRU for contents of bt2cnt. */
	ql_head(prof_thr_cnt_t)	lru_ql;

	/* Backtrace vector, used for calls to prof_backtrace(). */
	void			**vec;

	/* Sampling state. */
	uint64_t		prng_state;
	uint64_t		threshold;
	uint64_t		accum;

	/* State used to avoid dumping while operating on prof internals. */
	bool			enq;
	bool			enq_idump;
	bool			enq_gdump;
};

#endif /* JEMALLOC_H_STRUCTS */
/******************************************************************************/
#ifdef JEMALLOC_H_EXTERNS

extern bool	opt_prof;
/*
 * Even if opt_prof is true, sampling can be temporarily disabled by setting
 * opt_prof_active to false.  No locking is used when updating opt_prof_active,
 * so there are no guarantees regarding how long it will take for all threads
 * to notice state changes.
 */
extern bool	opt_prof_active;
extern size_t	opt_lg_prof_sample;   /* Mean bytes between samples. */
extern ssize_t	opt_lg_prof_interval; /* lg(prof_interval). */
extern bool	opt_prof_gdump;       /* High-water memory dumping. */
extern bool	opt_prof_final;       /* Final profile dumping. */
extern bool	opt_prof_leak;        /* Dump leak summary at exit. */
extern bool	opt_prof_accum;       /* Report cumulative bytes. */
extern char	opt_prof_prefix[PATH_MAX + 1];

/*
 * Profile dump interval, measured in bytes allocated.  Each arena triggers a
 * profile dump when it reaches this threshold.  The effect is that the
 * interval between profile dumps averages prof_interval, though the actual
 * interval between dumps will tend to be sporadic, and the interval will be a
 * maximum of approximately (prof_interval * narenas).
 */
extern uint64_t	prof_interval;

/*
 * If true, promote small sampled objects to large objects, since small run
 * headers do not have embedded profile context pointers.
 */
extern bool	prof_promote;

void	bt_init(prof_bt_t *bt, void **vec);
void	prof_backtrace(prof_bt_t *bt, unsigned nignore);
prof_thr_cnt_t	*prof_lookup(prof_bt_t *bt);
void	prof_idump(void);
bool	prof_mdump(const char *filename);
void	prof_gdump(void);
prof_tdata_t	*prof_tdata_init(void);
void	prof_tdata_cleanup(void *arg);
void	prof_boot0(void);
void	prof_boot1(void);
bool	prof_boot2(void);
void	prof_prefork(void);
void	prof_postfork_parent(void);
void	prof_postfork_child(void);

#endif /* JEMALLOC_H_EXTERNS */
/******************************************************************************/
#ifdef JEMALLOC_H_INLINES

#define	PROF_ALLOC_PREP(nignore, size, ret) do {			\
	prof_tdata_t *prof_tdata;					\
	prof_bt_t bt;							\
									\
	assert(size == s2u(size));					\
									\
	prof_tdata = prof_tdata_get(true);				\
	if ((uintptr_t)prof_tdata <= (uintptr_t)PROF_TDATA_STATE_MAX) {	\
		if (prof_tdata != NULL)					\
			ret = (prof_thr_cnt_t *)(uintptr_t)1U;		\
		else							\
			ret = NULL;					\
		break;							\
	}								\
									\
	if (opt_prof_active == false) {					\
		/* Sampling is currently inactive, so avoid sampling. */\
		ret = (prof_thr_cnt_t *)(uintptr_t)1U;			\
	} else if (opt_lg_prof_sample == 0) {				\
		/* Don't bother with sampling logic, since sampling   */\
		/* interval is 1.                                     */\
		bt_init(&bt, prof_tdata->vec);				\
		prof_backtrace(&bt, nignore);				\
		ret = prof_lookup(&bt);					\
	} else {							\
		if (prof_tdata->threshold == 0) {			\
			/* Initialize.  Seed the prng differently for */\
			/* each thread.                               */\
			prof_tdata->prng_state =			\
			    (uint64_t)(uintptr_t)&size;			\
			prof_sample_threshold_update(prof_tdata);	\
		}							\
									\
		/* Determine whether to capture a backtrace based on  */\
		/* whether size is enough for prof_accum to reach     */\
		/* prof_tdata->threshold.  However, delay updating    */\
		/* these variables until prof_{m,re}alloc(), because  */\
		/* we don't know for sure that the allocation will    */\
		/* succeed.                                           */\
		/*                                                    */\
		/* Use subtraction rather than addition to avoid      */\
		/* potential integer overflow.                        */\
		if (size >= prof_tdata->threshold -			\
		    prof_tdata->accum) {				\
			bt_init(&bt, prof_tdata->vec);			\
			prof_backtrace(&bt, nignore);			\
			ret = prof_lookup(&bt);				\
		} else							\
			ret = (prof_thr_cnt_t *)(uintptr_t)1U;		\
	}								\
} while (0)

#ifndef JEMALLOC_ENABLE_INLINE
malloc_tsd_protos(JEMALLOC_ATTR(unused), prof_tdata, prof_tdata_t *)

prof_tdata_t	*prof_tdata_get(bool create);
void	prof_sample_threshold_update(prof_tdata_t *prof_tdata);
prof_ctx_t	*prof_ctx_get(const void *ptr);
void	prof_ctx_set(const void *ptr, prof_ctx_t *ctx);
bool	prof_sample_accum_update(size_t size);
void	prof_malloc(const void *ptr, size_t size, prof_thr_cnt_t *cnt);
void	prof_realloc(const void *ptr, size_t size, prof_thr_cnt_t *cnt,
    size_t old_size, prof_ctx_t *old_ctx);
void	prof_free(const void *ptr, size_t size);
#endif

#if (defined(JEMALLOC_ENABLE_INLINE) || defined(JEMALLOC_PROF_C_))
/* Thread-specific backtrace cache, used to reduce bt2ctx contention. */
malloc_tsd_externs(prof_tdata, prof_tdata_t *)
malloc_tsd_funcs(JEMALLOC_INLINE, prof_tdata, prof_tdata_t *, NULL,
    prof_tdata_cleanup)

JEMALLOC_INLINE prof_tdata_t *
prof_tdata_get(bool create)
{
	prof_tdata_t *prof_tdata;

	cassert(config_prof);

	prof_tdata = *prof_tdata_tsd_get();
	if (create && prof_tdata == NULL)
		prof_tdata = prof_tdata_init();

	return (prof_tdata);
}

JEMALLOC_INLINE void
prof_sample_threshold_update(prof_tdata_t *prof_tdata)
{
	/*
	 * The body of this function is compiled out unless heap profiling is
	 * enabled, so that it is possible to compile jemalloc with floating
	 * point support completely disabled.  Avoiding floating point code is
	 * important on memory-constrained systems, but it also enables a
	 * workaround for versions of glibc that don't properly save/restore
	 * floating point registers during dynamic lazy symbol loading (which
	 * internally calls into whatever malloc implementation happens to be
	 * integrated into the application).  Note that some compilers (e.g.
	 * gcc 4.8) may use floating point registers for fast memory moves, so
	 * jemalloc must be compiled with such optimizations disabled (e.g.
	 * -mno-sse) in order for the workaround to be complete.
	 */
#ifdef JEMALLOC_PROF
	uint64_t r;
	double u;

	cassert(config_prof);

	/*
	 * Compute sample threshold as a geometrically distributed random
	 * variable with mean (2^opt_lg_prof_sample).
	 *
	 *                         __        __
	 *                         |  log(u)  |                     1
	 * prof_tdata->threshold = | -------- |, where p = -------------------
	 *                         | log(1-p) |             opt_lg_prof_sample
	 *                                                 2
	 *
	 * For more information on the math, see:
	 *
	 *   Non-Uniform Random Variate Generation
	 *   Luc Devroye
	 *   Springer-Verlag, New York, 1986
	 *   pp 500
	 *   (http://luc.devroye.org/rnbookindex.html)
	 */
	prng64(r, 53, prof_tdata->prng_state,
	    UINT64_C(6364136223846793005), UINT64_C(1442695040888963407));
	u = (double)r * (1.0/9007199254740992.0L);
	prof_tdata->threshold = (uint64_t)(log(u) /
	    log(1.0 - (1.0 / (double)((uint64_t)1U << opt_lg_prof_sample))))
	    + (uint64_t)1U;
#endif
}

JEMALLOC_INLINE prof_ctx_t *
prof_ctx_get(const void *ptr)
{
	prof_ctx_t *ret;
	arena_chunk_t *chunk;

	cassert(config_prof);
	assert(ptr != NULL);

	chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
	if (chunk != ptr) {
		/* Region. */
		ret = arena_prof_ctx_get(ptr);
	} else
		ret = huge_prof_ctx_get(ptr);

	return (ret);
}

JEMALLOC_INLINE void
prof_ctx_set(const void *ptr, prof_ctx_t *ctx)
{
	arena_chunk_t *chunk;

	cassert(config_prof);
	assert(ptr != NULL);

	chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
	if (chunk != ptr) {
		/* Region. */
		arena_prof_ctx_set(ptr, ctx);
	} else
		huge_prof_ctx_set(ptr, ctx);
}

JEMALLOC_INLINE bool
prof_sample_accum_update(size_t size)
{
	prof_tdata_t *prof_tdata;

	cassert(config_prof);
	/* Sampling logic is unnecessary if the interval is 1. */
	assert(opt_lg_prof_sample != 0);

	prof_tdata = prof_tdata_get(false);
	if ((uintptr_t)prof_tdata <= (uintptr_t)PROF_TDATA_STATE_MAX)
		return (true);

	/* Take care to avoid integer overflow. */
	if (size >= prof_tdata->threshold - prof_tdata->accum) {
		prof_tdata->accum -= (prof_tdata->threshold - size);
		/* Compute new sample threshold. */
		prof_sample_threshold_update(prof_tdata);
		while (prof_tdata->accum >= prof_tdata->threshold) {
			prof_tdata->accum -= prof_tdata->threshold;
			prof_sample_threshold_update(prof_tdata);
		}
		return (false);
	} else {
		prof_tdata->accum += size;
		return (true);
	}
}

JEMALLOC_INLINE void
prof_malloc(const void *ptr, size_t size, prof_thr_cnt_t *cnt)
{

	cassert(config_prof);
	assert(ptr != NULL);
	assert(size == isalloc(ptr, true));

	if (opt_lg_prof_sample != 0) {
		if (prof_sample_accum_update(size)) {
			/*
			 * Don't sample.  For malloc()-like allocation, it is
			 * always possible to tell in advance how large an
			 * object's usable size will be, so there should never
			 * be a difference between the size passed to
			 * PROF_ALLOC_PREP() and prof_malloc().
			 */
			assert((uintptr_t)cnt == (uintptr_t)1U);
		}
	}

	if ((uintptr_t)cnt > (uintptr_t)1U) {
		prof_ctx_set(ptr, cnt->ctx);

		cnt->epoch++;
		/*********/
		mb_write();
		/*********/
		cnt->cnts.curobjs++;
		cnt->cnts.curbytes += size;
		if (opt_prof_accum) {
			cnt->cnts.accumobjs++;
			cnt->cnts.accumbytes += size;
		}
		/*********/
		mb_write();
		/*********/
		cnt->epoch++;
		/*********/
		mb_write();
		/*********/
	} else
		prof_ctx_set(ptr, (prof_ctx_t *)(uintptr_t)1U);
}

JEMALLOC_INLINE void
prof_realloc(const void *ptr, size_t size, prof_thr_cnt_t *cnt,
    size_t old_size, prof_ctx_t *old_ctx)
{
	prof_thr_cnt_t *told_cnt;

	cassert(config_prof);
	assert(ptr != NULL || (uintptr_t)cnt <= (uintptr_t)1U);

	if (ptr != NULL) {
		assert(size == isalloc(ptr, true));
		if (opt_lg_prof_sample != 0) {
			if (prof_sample_accum_update(size)) {
				/*
				 * Don't sample.  The size passed to
				 * PROF_ALLOC_PREP() was larger than what
				 * actually got allocated, so a backtrace was
				 * captured for this allocation, even though
				 * its actual size was insufficient to cross
				 * the sample threshold.
				 */
				cnt = (prof_thr_cnt_t *)(uintptr_t)1U;
			}
		}
	}

	if ((uintptr_t)old_ctx > (uintptr_t)1U) {
		told_cnt = prof_lookup(old_ctx->bt);
		if (told_cnt == NULL) {
			/*
			 * It's too late to propagate OOM for this realloc(),
			 * so operate directly on old_cnt->ctx->cnt_merged.
			 */
			malloc_mutex_lock(old_ctx->lock);
			old_ctx->cnt_merged.curobjs--;
			old_ctx->cnt_merged.curbytes -= old_size;
			malloc_mutex_unlock(old_ctx->lock);
			told_cnt = (prof_thr_cnt_t *)(uintptr_t)1U;
		}
	} else
		told_cnt = (prof_thr_cnt_t *)(uintptr_t)1U;

	if ((uintptr_t)told_cnt > (uintptr_t)1U)
		told_cnt->epoch++;
	if ((uintptr_t)cnt > (uintptr_t)1U) {
		prof_ctx_set(ptr, cnt->ctx);
		cnt->epoch++;
	} else if (ptr != NULL)
		prof_ctx_set(ptr, (prof_ctx_t *)(uintptr_t)1U);
	/*********/
	mb_write();
	/*********/
	if ((uintptr_t)told_cnt > (uintptr_t)1U) {
		told_cnt->cnts.curobjs--;
		told_cnt->cnts.curbytes -= old_size;
	}
	if ((uintptr_t)cnt > (uintptr_t)1U) {
		cnt->cnts.curobjs++;
		cnt->cnts.curbytes += size;
		if (opt_prof_accum) {
			cnt->cnts.accumobjs++;
			cnt->cnts.accumbytes += size;
		}
	}
	/*********/
	mb_write();
	/*********/
	if ((uintptr_t)told_cnt > (uintptr_t)1U)
		told_cnt->epoch++;
	if ((uintptr_t)cnt > (uintptr_t)1U)
		cnt->epoch++;
	/*********/
	mb_write(); /* Not strictly necessary. */
}

JEMALLOC_INLINE void
prof_free(const void *ptr, size_t size)
{
	prof_ctx_t *ctx = prof_ctx_get(ptr);

	cassert(config_prof);

	if ((uintptr_t)ctx > (uintptr_t)1) {
		prof_thr_cnt_t *tcnt;
		assert(size == isalloc(ptr, true));
		tcnt = prof_lookup(ctx->bt);

		if (tcnt != NULL) {
			tcnt->epoch++;
			/*********/
			mb_write();
			/*********/
			tcnt->cnts.curobjs--;
			tcnt->cnts.curbytes -= size;
			/*********/
			mb_write();
			/*********/
			tcnt->epoch++;
			/*********/
			mb_write();
			/*********/
		} else {
			/*
			 * OOM during free() cannot be propagated, so operate
			 * directly on cnt->ctx->cnt_merged.
			 */
			malloc_mutex_lock(ctx->lock);
			ctx->cnt_merged.curobjs--;
			ctx->cnt_merged.curbytes -= size;
			malloc_mutex_unlock(ctx->lock);
		}
	}
}
#endif

#endif /* JEMALLOC_H_INLINES */
/******************************************************************************/