src/vppinfra/elog.h - fdio/vpp - Gitiles

 /*
  * Copyright (c) 2015 Cisco and/or its affiliates.
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 /*
   Copyright (c) 2005,2009 Eliot Dresselhaus

   Permission is hereby granted, free of charge, to any person obtaining
   a copy of this software and associated documentation files (the
   "Software"), to deal in the Software without restriction, including
   without limitation the rights to use, copy, modify, merge, publish,
   distribute, sublicense, and/or sell copies of the Software, and to
   permit persons to whom the Software is furnished to do so, subject to
   the following conditions:

   The above copyright notice and this permission notice shall be
   included in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
   LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
   OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
   WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

 /* High speed event logger */

 /** \file
     The fine-grained event logger allows lightweight, thread-safe
     event logging at minimum cost. In typical operation, logging
     a single event costs around 80ns on x86_64. It's appropriate
     for at-least per-frame event-logging in vector packet processing.

     See https://wiki.fd.io/view/VPP/elog for more information.
 */

 #ifndef included_clib_elog_h
 #define included_clib_elog_h

 #include <vppinfra/cache.h>
 #include <vppinfra/error.h>	/* for ASSERT */
 #include <vppinfra/serialize.h>
 #include <vppinfra/time.h>	/* for clib_cpu_time_now */
 #include <vppinfra/hash.h>
 #include <vppinfra/mhash.h>

 typedef struct
 {
   union
   {
     /** Absolute time stamp in CPU clock cycles. */
     u64 time_cycles;

     /** Absolute time as floating point number in seconds. */
     f64 time;
   };

   /** Event type index. */
   u16 type;

   /** Track for this event.  Tracks allow events to be sorted and
      displayed by track.  Think of 2 dimensional display with time and
      track being the x and y axes. */
   u16 track;

   /** 20-bytes of data follows, pads to 32 bytes. */
   u8 data[20];
 } elog_event_t;

 typedef struct
 {
   /** Type index plus one assigned to this type.
      This is used to mark type as seen. */
   u32 type_index_plus_one;

   /** String table as a vector constructed when type is registered. */
   char **enum_strings_vector;

   /** Format string. (example: "my-event (%d,%d)"). */
   char *format;

   /** Specifies how arguments to format are parsed from event data.
      String of characters '0' '1' or '2' '3' to specify log2 size of data
      (e.g. for u8, u16, u32 or u64),
      's' means a null-terminated C string
      't' means argument is an index into enum string table for this type.
      'e' is a float,
      'f' is a double. */
   char *format_args;

   /** Function name generating event. */
   char *function;

   /** Number of elements in string enum table. */
   u32 n_enum_strings;

   /** String table for enum/number to string formatting. */
   char *enum_strings[];
 } elog_event_type_t;

 typedef struct
 {
   /** Track name vector. */
   char *name;

   /** Set to one when track has been added to
      main structure. */
   u32 track_index_plus_one;
 } elog_track_t;

 typedef struct
 {
   /** CPU cycle counter. */
   u64 cpu;

   /** OS timer in nano secs since epoch 3/30/2017, see elog_time_now() */
   u64 os_nsec;
 } elog_time_stamp_t;

 typedef struct
 {
   /** Total number of events in buffer. */
   u32 n_total_events;

   /** When count reaches limit logging is disabled.  This is
      used for event triggers. */
   u32 n_total_events_disable_limit;

   /** Dummy event to use when logger is disabled. */
   elog_event_t placeholder_event;

   /** Power of 2 number of elements in ring. */
   uword event_ring_size;

   /** Vector of events (circular buffer).  Power of 2 size.
       Used when events are being collected. */
   elog_event_t *event_ring;

   /** Vector of event types. */
   elog_event_type_t *event_types;

   /** Hash table mapping type format to type index. */
   uword *event_type_by_format;

   /** Events may refer to strings in string table. */
   char *string_table;
   uword *string_table_hash;
   u8 *string_table_tmp;

   /** Vector of tracks. */
   elog_track_t *tracks;

   /** Default track. */
   elog_track_t default_track;

   /** Place holder for CPU clock frequency. */
   clib_time_t cpu_timer;

   /** Timestamps */
   elog_time_stamp_t init_time, serialize_time;

   /** SMP lock, non-zero means locking required */
   uword *lock;

   /** Use serialize_time and init_time to give estimate for
       cpu clock frequency. */
   f64 nsec_per_cpu_clock;

   /** Vector of events converted to generic form after collection. */
   elog_event_t *events;
 } elog_main_t;

 /** @brief Return number of events in the event-log buffer
     @param em elog_main_t *
     @return number of events in the buffer
 */

 always_inline uword
 elog_n_events_in_buffer (elog_main_t * em)
 {
   return clib_min (em->n_total_events, em->event_ring_size);
 }

 /** @brief Return number of events which can fit in the event buffer
     @param em elog_main_t *
     @return number of events which can fit in the buffer
 */
 always_inline uword
 elog_buffer_capacity (elog_main_t * em)
 {
   return em->event_ring_size;
 }

 /** @brief Reset the event buffer
     @param em elog_main_t *
 */
 always_inline void
 elog_reset_buffer (elog_main_t * em)
 {
   em->n_total_events = 0;
   em->n_total_events_disable_limit = ~0;
 }

 /** @brief Enable or disable event logging
     @param em elog_main_t *
 */
 always_inline void
 elog_enable_disable (elog_main_t * em, int is_enabled)
 {
   em->n_total_events = 0;
   em->n_total_events_disable_limit = is_enabled ? ~0 : 0;
 }

 /** @brief disable logging after specified number of ievents have been logged.

    This is used as a "debug trigger" when a certain event has occurred.
    Events will be logged both before and after the "event" but the
    event will not be lost as long as N < RING_SIZE.

    @param em elog_main_t *
    @param n uword number of events before disabling event logging
 */
 always_inline void
 elog_disable_after_events (elog_main_t * em, uword n)
 {
   em->n_total_events_disable_limit = em->n_total_events + n;
 }

 /* @brief mid-buffer logic-analyzer trigger

    Currently, only midpoint triggering is supported, but it's pretty obvious
    how to generalize the scheme.
    @param em elog_main_t *
 */
 always_inline void
 elog_disable_trigger (elog_main_t * em)
 {
   em->n_total_events_disable_limit =
     em->n_total_events + vec_len (em->event_ring) / 2;
 }

 /** @brief register an event type
     @param em elog_main_t *
     @param t elog_event_type_t * event to register
     @return type index
     @warning Typically not called directly
 */

 word elog_event_type_register (elog_main_t * em, elog_event_type_t * t);

 /** @brief register an event track
     @param em elog_main_t *
     @param t elog_track_t * track to register
     @return track index
     @note this function is often called directly
 */
 word elog_track_register (elog_main_t * em, elog_track_t * t);

 /** @brief event logging enabled predicate
     @param em elog_main_t *
     @return 1 if enabled, 0 if not enabled
 */
 always_inline uword
 elog_is_enabled (elog_main_t * em)
 {
   return em->n_total_events < em->n_total_events_disable_limit;
 }

 /** @brief Allocate an event to be filled in by the caller

     Not normally called directly; this function underlies the
     ELOG_DATA and ELOG_TRACK_DATA macros

     @param em elog_main_t *
     @param type elog_event_type_t * type
     @param track elog_track_t * track
     @param cpu_time u64 current cpu tick value
     @returns event to be filled in
 */
 always_inline void *
 elog_event_data_inline (elog_main_t * em,
 			elog_event_type_t * type,
 			elog_track_t * track, u64 cpu_time)
 {
   elog_event_t *e;
   uword ei;
   word type_index, track_index;

   /* Return the user placeholder memory to scribble data into. */
   if (PREDICT_FALSE (!elog_is_enabled (em)))
     return em->placeholder_event.data;

   type_index = (word) type->type_index_plus_one - 1;
   track_index = (word) track->track_index_plus_one - 1;
   if (PREDICT_FALSE ((type_index | track_index) < 0))
     {
       if (type_index < 0)
 	type_index = elog_event_type_register (em, type);
       if (track_index < 0)
 	track_index = elog_track_register (em, track);
     }

   ASSERT (track_index < vec_len (em->tracks));
   ASSERT (is_pow2 (vec_len (em->event_ring)));

   if (em->lock)
     ei = clib_atomic_fetch_add (&em->n_total_events, 1);
   else
     ei = em->n_total_events++;

   ei &= em->event_ring_size - 1;
   e = vec_elt_at_index (em->event_ring, ei);

   e->time_cycles = cpu_time;
   e->type = type_index;
   e->track = track_index;

   /* Return user data for caller to fill in. */
   return e->data;
 }

 /* External version of inline. */
 void *elog_event_data (elog_main_t * em,
 		       elog_event_type_t * type,
 		       elog_track_t * track, u64 cpu_time);

 /** @brief Allocate an event to be filled in by the caller, non-inline

     Not normally called directly; this function underlies the
     ELOG_DATA and ELOG_TRACK_DATA macros

     @param em elog_main_t *
     @param type elog_event_type_t * type
     @param track elog_track_t * track
     @param cpu_time u64 current cpu tick value
     @returns event to be filled in
 */
 always_inline void *
 elog_event_data_not_inline (elog_main_t * em,
 			    elog_event_type_t * type,
 			    elog_track_t * track, u64 cpu_time)
 {
   /* Return the user placeholder memory to scribble data into. */
   if (PREDICT_FALSE (!elog_is_enabled (em)))
     return em->placeholder_event.data;
   return elog_event_data (em, type, track, cpu_time);
 }

 /** @brief Log a single-datum event
     @param em elog_main_t *
     @param type elog_event_type_t * type
     @param data u32 single datum to capture
 */
 always_inline void
 elog (elog_main_t * em, elog_event_type_t * type, u32 data)
 {
   u32 *d = elog_event_data_not_inline (em,
 				       type,
 				       &em->default_track,
 				       clib_cpu_time_now ());
   d[0] = data;
 }

 /** @brief Log a single-datum event, inline version
     @param em elog_main_t *
     @param type elog_event_type_t * type
     @param data u32 single datum to capture
 */
 always_inline void
 elog_inline (elog_main_t * em, elog_event_type_t * type, u32 data)
 {
   u32 *d = elog_event_data_inline (em,
 				   type,
 				   &em->default_track,
 				   clib_cpu_time_now ());
   d[0] = data;
 }

 /** @brief Log a single-datum event to a specific track, non-inline version
     @param em elog_main_t *
     @param type elog_event_type_t * type
     @param type elog_event_track_t * track
     @param data u32 single datum to capture
 */
 always_inline void
 elog_track (elog_main_t * em, elog_event_type_t * type, elog_track_t * track,
 	    u32 data)
 {
   u32 *d = elog_event_data_not_inline (em,
 				       type,
 				       track,
 				       clib_cpu_time_now ());
   d[0] = data;
 }

 /** @brief Log a single-datum event to a specific track
     @param em elog_main_t *
     @param type elog_event_type_t * type
     @param type elog_event_track_t * track
     @param data u32 single datum to capture
 */
 always_inline void
 elog_track_inline (elog_main_t * em, elog_event_type_t * type,
 		   elog_track_t * track, u32 data)
 {
   u32 *d = elog_event_data_inline (em,
 				   type,
 				   track,
 				   clib_cpu_time_now ());
   d[0] = data;
 }

 always_inline void *
 elog_data (elog_main_t * em, elog_event_type_t * type, elog_track_t * track)
 {
   return elog_event_data_not_inline (em, type, track, clib_cpu_time_now ());
 }

 always_inline void *
 elog_data_inline (elog_main_t * em, elog_event_type_t * type,
 		  elog_track_t * track)
 {
   return elog_event_data_inline (em, type, track, clib_cpu_time_now ());
 }

 /* Macro shorthands for generating/declaring events. */
 #define __ELOG_TYPE_VAR(f) f
 #define __ELOG_TRACK_VAR(f) f

 #define ELOG_TYPE_DECLARE(f) static elog_event_type_t __ELOG_TYPE_VAR(f)

 #define ELOG_TYPE_INIT_FORMAT_AND_FUNCTION(fmt,func) \
   { .format = fmt, .function = func, }

 #define ELOG_TYPE_INIT(fmt) \
   ELOG_TYPE_INIT_FORMAT_AND_FUNCTION(fmt,(char *) __FUNCTION__)

 #define ELOG_TYPE_DECLARE_HELPER(f,fmt,func)		\
   static elog_event_type_t __ELOG_TYPE_VAR(f) =		\
     ELOG_TYPE_INIT_FORMAT_AND_FUNCTION (fmt, func)

 #define ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION(f,fmt)		\
   ELOG_TYPE_DECLARE_HELPER (f, fmt, (char *) __FUNCTION__)

 #define ELOG_TYPE_DECLARE_FORMAT(f,fmt)		\
   ELOG_TYPE_DECLARE_HELPER (f, fmt, 0)

 /* Shorthands with and without __FUNCTION__.
    D for decimal; X for hex.  F for __FUNCTION__. */
 #define ELOG_TYPE(f,fmt) ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION(f,fmt)
 #define ELOG_TYPE_D(f)  ELOG_TYPE_DECLARE_FORMAT (f, #f " %d")
 #define ELOG_TYPE_X(f)  ELOG_TYPE_DECLARE_FORMAT (f, #f " 0x%x")
 #define ELOG_TYPE_DF(f) ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION (f, #f " %d")
 #define ELOG_TYPE_XF(f) ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION (f, #f " 0x%x")
 #define ELOG_TYPE_FD(f) ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION (f, #f " %d")
 #define ELOG_TYPE_FX(f) ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION (f, #f " 0x%x")

 #define ELOG_TRACK_DECLARE(f) static elog_track_t __ELOG_TRACK_VAR(f)
 #define ELOG_TRACK(f) ELOG_TRACK_DECLARE(f) = { .name = #f, }

 /* Log 32 bits of data. */
 #define ELOG(em,f,data) elog ((em), &__ELOG_TYPE_VAR(f), data)
 #define ELOG_INLINE(em,f,data) elog_inline ((em), &__ELOG_TYPE_VAR(f), data)

 /* Return data pointer to fill in. */
 #define ELOG_TRACK_DATA(em,f,track) \
   elog_data ((em), &__ELOG_TYPE_VAR(f), &__ELOG_TRACK_VAR(track))
 #define ELOG_TRACK_DATA_INLINE(em,f,track) \
   elog_data_inline ((em), &__ELOG_TYPE_VAR(f), &__ELOG_TRACK_VAR(track))

 /* Shorthand with default track. */
 #define ELOG_DATA(em,f) elog_data ((em), &__ELOG_TYPE_VAR (f), &(em)->default_track)
 #define ELOG_DATA_INLINE(em,f) elog_data_inline ((em), &__ELOG_TYPE_VAR (f), &(em)->default_track)

 /** @brief add a string to the event-log string table

     Often combined with hashing and the T4 elog format specifier to
     display complex strings in offline tooling

     @param em elog_main_t *
     @param format char *
     @param VARARGS
     @return u32 index to add to event log
 */
 u32 elog_string (elog_main_t * em, char *format, ...);

 void elog_time_now (elog_time_stamp_t * et);

 /** @brief convert event ring events to events, and return them as a vector.
     @param em elog_main_t *
     @return event vector with timestamps in f64 seconds
     @note sets em->events to resulting vector.
 */
 elog_event_t *elog_get_events (elog_main_t * em);

 /** @brief convert event ring events to events, and return them as a vector.
     @param em elog_main_t *
     @return event vector with timestamps in f64 seconds
     @note no side effects
 */
 elog_event_t *elog_peek_events (elog_main_t * em);

 /* Merge two logs, add supplied track tags. */
 void elog_merge (elog_main_t * dst, u8 * dst_tag,
 		 elog_main_t * src, u8 * src_tag, f64 align_tweak);

 /* 2 arguments elog_main_t and elog_event_t to format event or track name. */
 u8 *format_elog_event (u8 * s, va_list * va);
 u8 *format_elog_track_name (u8 * s, va_list * va);
 u8 *format_elog_track (u8 * s, va_list * args);

 void serialize_elog_main (serialize_main_t * m, va_list * va);
 void unserialize_elog_main (serialize_main_t * m, va_list * va);

 void elog_init (elog_main_t * em, u32 n_events);
 void elog_alloc (elog_main_t * em, u32 n_events);

 #ifdef CLIB_UNIX
 always_inline clib_error_t *
 elog_write_file (elog_main_t * em, char *clib_file, int flush_ring)
 {
   serialize_main_t m;
   clib_error_t *error;

   error = serialize_open_clib_file (&m, clib_file);
   if (error)
     return error;
   error = serialize (&m, serialize_elog_main, em, flush_ring);
   if (!error)
     serialize_close (&m);
   return error;
 }

 always_inline clib_error_t *
 elog_read_file (elog_main_t * em, char *clib_file)
 {
   serialize_main_t m;
   clib_error_t *error;

   error = unserialize_open_clib_file (&m, clib_file);
   if (error)
     return error;
   error = unserialize (&m, unserialize_elog_main, em);
   if (!error)
     unserialize_close (&m);
   return error;
 }

 #endif /* CLIB_UNIX */

 #endif /* included_clib_elog_h */

 /*
  * fd.io coding-style-patch-verification: ON
  *
  * Local Variables:
  * eval: (c-set-style "gnu")
  * End:
  */
	/*
	* Copyright (c) 2015 Cisco and/or its affiliates.
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at:
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	/*
	Copyright (c) 2005,2009 Eliot Dresselhaus

	Permission is hereby granted, free of charge, to any person obtaining
	a copy of this software and associated documentation files (the
	"Software"), to deal in the Software without restriction, including
	without limitation the rights to use, copy, modify, merge, publish,
	distribute, sublicense, and/or sell copies of the Software, and to
	permit persons to whom the Software is furnished to do so, subject to
	the following conditions:

	The above copyright notice and this permission notice shall be
	included in all copies or substantial portions of the Software.

	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
	NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
	LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
	OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
	WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
	*/

	/* High speed event logger */

	/** \file
	The fine-grained event logger allows lightweight, thread-safe
	event logging at minimum cost. In typical operation, logging
	a single event costs around 80ns on x86_64. It's appropriate
	for at-least per-frame event-logging in vector packet processing.

	See https://wiki.fd.io/view/VPP/elog for more information.
	*/

	#ifndef included_clib_elog_h
	#define included_clib_elog_h

	#include <vppinfra/cache.h>
	#include <vppinfra/error.h> /* for ASSERT */
	#include <vppinfra/serialize.h>
	#include <vppinfra/time.h> /* for clib_cpu_time_now */
	#include <vppinfra/hash.h>
	#include <vppinfra/mhash.h>

	typedef struct
	{
	union
	{
	/** Absolute time stamp in CPU clock cycles. */
	u64 time_cycles;

	/** Absolute time as floating point number in seconds. */
	f64 time;
	};

	/** Event type index. */
	u16 type;

	/** Track for this event. Tracks allow events to be sorted and
	displayed by track. Think of 2 dimensional display with time and
	track being the x and y axes. */
	u16 track;

	/** 20-bytes of data follows, pads to 32 bytes. */
	u8 data[20];
	} elog_event_t;

	typedef struct
	{
	/** Type index plus one assigned to this type.
	This is used to mark type as seen. */
	u32 type_index_plus_one;

	/** String table as a vector constructed when type is registered. */
	char **enum_strings_vector;

	/** Format string. (example: "my-event (%d,%d)"). */
	char *format;

	/** Specifies how arguments to format are parsed from event data.
	String of characters '0' '1' or '2' '3' to specify log2 size of data
	(e.g. for u8, u16, u32 or u64),
	's' means a null-terminated C string
	't' means argument is an index into enum string table for this type.
	'e' is a float,
	'f' is a double. */
	char *format_args;

	/** Function name generating event. */
	char *function;

	/** Number of elements in string enum table. */
	u32 n_enum_strings;

	/** String table for enum/number to string formatting. */
	char *enum_strings[];
	} elog_event_type_t;

	typedef struct
	{
	/** Track name vector. */
	char *name;

	/** Set to one when track has been added to
	main structure. */
	u32 track_index_plus_one;
	} elog_track_t;

	typedef struct
	{
	/** CPU cycle counter. */
	u64 cpu;

	/** OS timer in nano secs since epoch 3/30/2017, see elog_time_now() */
	u64 os_nsec;
	} elog_time_stamp_t;

	typedef struct
	{
	/** Total number of events in buffer. */
	u32 n_total_events;

	/** When count reaches limit logging is disabled. This is
	used for event triggers. */
	u32 n_total_events_disable_limit;

	/** Dummy event to use when logger is disabled. */
	elog_event_t placeholder_event;

	/** Power of 2 number of elements in ring. */
	uword event_ring_size;

	/** Vector of events (circular buffer). Power of 2 size.
	Used when events are being collected. */
	elog_event_t *event_ring;

	/** Vector of event types. */
	elog_event_type_t *event_types;

	/** Hash table mapping type format to type index. */
	uword *event_type_by_format;

	/** Events may refer to strings in string table. */
	char *string_table;
	uword *string_table_hash;
	u8 *string_table_tmp;

	/** Vector of tracks. */
	elog_track_t *tracks;

	/** Default track. */
	elog_track_t default_track;

	/** Place holder for CPU clock frequency. */
	clib_time_t cpu_timer;

	/** Timestamps */
	elog_time_stamp_t init_time, serialize_time;

	/** SMP lock, non-zero means locking required */
	uword *lock;

	/** Use serialize_time and init_time to give estimate for
	cpu clock frequency. */
	f64 nsec_per_cpu_clock;

	/** Vector of events converted to generic form after collection. */
	elog_event_t *events;
	} elog_main_t;

	/** @brief Return number of events in the event-log buffer
	@param em elog_main_t *
	@return number of events in the buffer
	*/

	always_inline uword
	elog_n_events_in_buffer (elog_main_t * em)
	{
	return clib_min (em->n_total_events, em->event_ring_size);
	}

	/** @brief Return number of events which can fit in the event buffer
	@param em elog_main_t *
	@return number of events which can fit in the buffer
	*/
	always_inline uword
	elog_buffer_capacity (elog_main_t * em)
	{
	return em->event_ring_size;
	}

	/** @brief Reset the event buffer
	@param em elog_main_t *
	*/
	always_inline void
	elog_reset_buffer (elog_main_t * em)
	{
	em->n_total_events = 0;
	em->n_total_events_disable_limit = ~0;
	}

	/** @brief Enable or disable event logging
	@param em elog_main_t *
	*/
	always_inline void
	elog_enable_disable (elog_main_t * em, int is_enabled)
	{
	em->n_total_events = 0;
	em->n_total_events_disable_limit = is_enabled ? ~0 : 0;
	}

	/** @brief disable logging after specified number of ievents have been logged.

	This is used as a "debug trigger" when a certain event has occurred.
	Events will be logged both before and after the "event" but the
	event will not be lost as long as N < RING_SIZE.

	@param em elog_main_t *
	@param n uword number of events before disabling event logging
	*/
	always_inline void
	elog_disable_after_events (elog_main_t * em, uword n)
	{
	em->n_total_events_disable_limit = em->n_total_events + n;
	}

	/* @brief mid-buffer logic-analyzer trigger

	Currently, only midpoint triggering is supported, but it's pretty obvious
	how to generalize the scheme.
	@param em elog_main_t *
	*/
	always_inline void
	elog_disable_trigger (elog_main_t * em)
	{
	em->n_total_events_disable_limit =
	em->n_total_events + vec_len (em->event_ring) / 2;
	}

	/** @brief register an event type
	@param em elog_main_t *
	@param t elog_event_type_t * event to register
	@return type index
	@warning Typically not called directly
	*/

	word elog_event_type_register (elog_main_t * em, elog_event_type_t * t);

	/** @brief register an event track
	@param em elog_main_t *
	@param t elog_track_t * track to register
	@return track index
	@note this function is often called directly
	*/
	word elog_track_register (elog_main_t * em, elog_track_t * t);

	/** @brief event logging enabled predicate
	@param em elog_main_t *
	@return 1 if enabled, 0 if not enabled
	*/
	always_inline uword
	elog_is_enabled (elog_main_t * em)
	{
	return em->n_total_events < em->n_total_events_disable_limit;
	}

	/** @brief Allocate an event to be filled in by the caller

	Not normally called directly; this function underlies the
	ELOG_DATA and ELOG_TRACK_DATA macros

	@param em elog_main_t *
	@param type elog_event_type_t * type
	@param track elog_track_t * track
	@param cpu_time u64 current cpu tick value
	@returns event to be filled in
	*/
	always_inline void *
	elog_event_data_inline (elog_main_t * em,
	elog_event_type_t * type,
	elog_track_t * track, u64 cpu_time)
	{
	elog_event_t *e;
	uword ei;
	word type_index, track_index;

	/* Return the user placeholder memory to scribble data into. */
	if (PREDICT_FALSE (!elog_is_enabled (em)))
	return em->placeholder_event.data;

	type_index = (word) type->type_index_plus_one - 1;
	track_index = (word) track->track_index_plus_one - 1;
	if (PREDICT_FALSE ((type_index \| track_index) < 0))
	{
	if (type_index < 0)
	type_index = elog_event_type_register (em, type);
	if (track_index < 0)
	track_index = elog_track_register (em, track);
	}

	ASSERT (track_index < vec_len (em->tracks));
	ASSERT (is_pow2 (vec_len (em->event_ring)));

	if (em->lock)
	ei = clib_atomic_fetch_add (&em->n_total_events, 1);
	else
	ei = em->n_total_events++;

	ei &= em->event_ring_size - 1;
	e = vec_elt_at_index (em->event_ring, ei);

	e->time_cycles = cpu_time;
	e->type = type_index;
	e->track = track_index;

	/* Return user data for caller to fill in. */
	return e->data;
	}

	/* External version of inline. */
	void elog_event_data (elog_main_t em,
	elog_event_type_t * type,
	elog_track_t * track, u64 cpu_time);

	/** @brief Allocate an event to be filled in by the caller, non-inline

	Not normally called directly; this function underlies the
	ELOG_DATA and ELOG_TRACK_DATA macros

	@param em elog_main_t *
	@param type elog_event_type_t * type
	@param track elog_track_t * track
	@param cpu_time u64 current cpu tick value
	@returns event to be filled in
	*/
	always_inline void *
	elog_event_data_not_inline (elog_main_t * em,
	elog_event_type_t * type,
	elog_track_t * track, u64 cpu_time)
	{
	/* Return the user placeholder memory to scribble data into. */
	if (PREDICT_FALSE (!elog_is_enabled (em)))
	return em->placeholder_event.data;
	return elog_event_data (em, type, track, cpu_time);
	}

	/** @brief Log a single-datum event
	@param em elog_main_t *
	@param type elog_event_type_t * type
	@param data u32 single datum to capture
	*/
	always_inline void
	elog (elog_main_t * em, elog_event_type_t * type, u32 data)
	{
	u32 *d = elog_event_data_not_inline (em,
	type,
	&em->default_track,
	clib_cpu_time_now ());
	d[0] = data;
	}

	/** @brief Log a single-datum event, inline version
	@param em elog_main_t *
	@param type elog_event_type_t * type
	@param data u32 single datum to capture
	*/
	always_inline void
	elog_inline (elog_main_t * em, elog_event_type_t * type, u32 data)
	{
	u32 *d = elog_event_data_inline (em,
	type,
	&em->default_track,
	clib_cpu_time_now ());
	d[0] = data;
	}

	/** @brief Log a single-datum event to a specific track, non-inline version
	@param em elog_main_t *
	@param type elog_event_type_t * type
	@param type elog_event_track_t * track
	@param data u32 single datum to capture
	*/
	always_inline void
	elog_track (elog_main_t * em, elog_event_type_t * type, elog_track_t * track,
	u32 data)
	{
	u32 *d = elog_event_data_not_inline (em,
	type,
	track,
	clib_cpu_time_now ());
	d[0] = data;
	}

	/** @brief Log a single-datum event to a specific track
	@param em elog_main_t *
	@param type elog_event_type_t * type
	@param type elog_event_track_t * track
	@param data u32 single datum to capture
	*/
	always_inline void
	elog_track_inline (elog_main_t * em, elog_event_type_t * type,
	elog_track_t * track, u32 data)
	{
	u32 *d = elog_event_data_inline (em,
	type,
	track,
	clib_cpu_time_now ());
	d[0] = data;
	}

	always_inline void *
	elog_data (elog_main_t * em, elog_event_type_t * type, elog_track_t * track)
	{
	return elog_event_data_not_inline (em, type, track, clib_cpu_time_now ());
	}

	always_inline void *
	elog_data_inline (elog_main_t * em, elog_event_type_t * type,
	elog_track_t * track)
	{
	return elog_event_data_inline (em, type, track, clib_cpu_time_now ());
	}

	/* Macro shorthands for generating/declaring events. */
	#define __ELOG_TYPE_VAR(f) f
	#define __ELOG_TRACK_VAR(f) f

	#define ELOG_TYPE_DECLARE(f) static elog_event_type_t __ELOG_TYPE_VAR(f)

	#define ELOG_TYPE_INIT_FORMAT_AND_FUNCTION(fmt,func) \
	{ .format = fmt, .function = func, }

	#define ELOG_TYPE_INIT(fmt) \
	ELOG_TYPE_INIT_FORMAT_AND_FUNCTION(fmt,(char *) __FUNCTION__)

	#define ELOG_TYPE_DECLARE_HELPER(f,fmt,func) \
	static elog_event_type_t __ELOG_TYPE_VAR(f) = \
	ELOG_TYPE_INIT_FORMAT_AND_FUNCTION (fmt, func)

	#define ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION(f,fmt) \
	ELOG_TYPE_DECLARE_HELPER (f, fmt, (char *) __FUNCTION__)

	#define ELOG_TYPE_DECLARE_FORMAT(f,fmt) \
	ELOG_TYPE_DECLARE_HELPER (f, fmt, 0)

	/* Shorthands with and without __FUNCTION__.
	D for decimal; X for hex. F for __FUNCTION__. */
	#define ELOG_TYPE(f,fmt) ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION(f,fmt)
	#define ELOG_TYPE_D(f) ELOG_TYPE_DECLARE_FORMAT (f, #f " %d")
	#define ELOG_TYPE_X(f) ELOG_TYPE_DECLARE_FORMAT (f, #f " 0x%x")
	#define ELOG_TYPE_DF(f) ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION (f, #f " %d")
	#define ELOG_TYPE_XF(f) ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION (f, #f " 0x%x")
	#define ELOG_TYPE_FD(f) ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION (f, #f " %d")
	#define ELOG_TYPE_FX(f) ELOG_TYPE_DECLARE_FORMAT_AND_FUNCTION (f, #f " 0x%x")

	#define ELOG_TRACK_DECLARE(f) static elog_track_t __ELOG_TRACK_VAR(f)
	#define ELOG_TRACK(f) ELOG_TRACK_DECLARE(f) = { .name = #f, }

	/* Log 32 bits of data. */
	#define ELOG(em,f,data) elog ((em), &__ELOG_TYPE_VAR(f), data)
	#define ELOG_INLINE(em,f,data) elog_inline ((em), &__ELOG_TYPE_VAR(f), data)

	/* Return data pointer to fill in. */
	#define ELOG_TRACK_DATA(em,f,track) \
	elog_data ((em), &__ELOG_TYPE_VAR(f), &__ELOG_TRACK_VAR(track))
	#define ELOG_TRACK_DATA_INLINE(em,f,track) \
	elog_data_inline ((em), &__ELOG_TYPE_VAR(f), &__ELOG_TRACK_VAR(track))

	/* Shorthand with default track. */
	#define ELOG_DATA(em,f) elog_data ((em), &__ELOG_TYPE_VAR (f), &(em)->default_track)
	#define ELOG_DATA_INLINE(em,f) elog_data_inline ((em), &__ELOG_TYPE_VAR (f), &(em)->default_track)

	/** @brief add a string to the event-log string table

	Often combined with hashing and the T4 elog format specifier to
	display complex strings in offline tooling

	@param em elog_main_t *
	@param format char *
	@param VARARGS
	@return u32 index to add to event log
	*/
	u32 elog_string (elog_main_t * em, char *format, ...);

	void elog_time_now (elog_time_stamp_t * et);

	/** @brief convert event ring events to events, and return them as a vector.
	@param em elog_main_t *
	@return event vector with timestamps in f64 seconds
	@note sets em->events to resulting vector.
	*/
	elog_event_t elog_get_events (elog_main_t em);

	/** @brief convert event ring events to events, and return them as a vector.
	@param em elog_main_t *
	@return event vector with timestamps in f64 seconds
	@note no side effects
	*/
	elog_event_t elog_peek_events (elog_main_t em);

	/* Merge two logs, add supplied track tags. */
	void elog_merge (elog_main_t * dst, u8 * dst_tag,
	elog_main_t * src, u8 * src_tag, f64 align_tweak);

	/* 2 arguments elog_main_t and elog_event_t to format event or track name. */
	u8 format_elog_event (u8 s, va_list * va);
	u8 format_elog_track_name (u8 s, va_list * va);
	u8 format_elog_track (u8 s, va_list * args);

	void serialize_elog_main (serialize_main_t * m, va_list * va);
	void unserialize_elog_main (serialize_main_t * m, va_list * va);

	void elog_init (elog_main_t * em, u32 n_events);
	void elog_alloc (elog_main_t * em, u32 n_events);

	#ifdef CLIB_UNIX
	always_inline clib_error_t *
	elog_write_file (elog_main_t * em, char *clib_file, int flush_ring)
	{
	serialize_main_t m;
	clib_error_t *error;

	error = serialize_open_clib_file (&m, clib_file);
	if (error)
	return error;
	error = serialize (&m, serialize_elog_main, em, flush_ring);
	if (!error)
	serialize_close (&m);
	return error;
	}

	always_inline clib_error_t *
	elog_read_file (elog_main_t * em, char *clib_file)
	{
	serialize_main_t m;
	clib_error_t *error;

	error = unserialize_open_clib_file (&m, clib_file);
	if (error)
	return error;
	error = unserialize (&m, unserialize_elog_main, em);
	if (!error)
	unserialize_close (&m);
	return error;
	}

	#endif /* CLIB_UNIX */

	#endif /* included_clib_elog_h */

	/*
	* fd.io coding-style-patch-verification: ON
	*
	* Local Variables:
	* eval: (c-set-style "gnu")
	* End:
	*/