ut0ut.h

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/** @file include/ut0ut.h
 Various utilities
 
 Created 1/20/1994 Heikki Tuuri
 ***********************************************************************/
 
/**************************************************/ /**
 @page PAGE_INNODB_UTILS Innodb utils
 
 Useful data structures:
 - @ref Link_buf - to track concurrent operations
 - @ref Sharded_rw_lock - sharded rw-lock (very fast s-lock, slow x-lock)
 
 *******************************************************/
 
#ifndef ut0ut_h
#define ut0ut_h
 
/* Do not include univ.i because univ.i includes this. */
 
#include <string.h>
#include <algorithm>
#include <chrono>
#include <cmath>
#include <iomanip>
#include <iterator>
#include <ostream>
#include <sstream>
#include <thread>
#include <type_traits>
 
#ifdef UNIV_DEBUG
#include <limits>
#include <random>
#endif /* UNIV_DEBUG */
 
#include "db0err.h"
 
#ifndef UNIV_HOTBACKUP
#include "os0atomic.h"
#endif /* !UNIV_HOTBACKUP */
 
#include <time.h>
 
#include <ctype.h>
 
#include <stdarg.h>
#include "ut/ut.h"
#include "ut0dbg.h"
 
#ifndef UNIV_NO_ERR_MSGS
#include "mysql/components/services/log_builtins.h"
#include "mysqld_error.h"
#include "sql/derror.h"
#endif /* !UNIV_NO_ERR_MSGS */
 
#ifndef UNIV_HOTBACKUP
#if defined(HAVE_PAUSE_INSTRUCTION)
/* According to the gcc info page, asm volatile means that the
instruction has important side-effects and must not be removed.
Also asm volatile may trigger a memory barrier (spilling all registers
to memory). */
#define UT_RELAX_CPU() __asm__ __volatile__("pause")
 
#elif defined(HAVE_FAKE_PAUSE_INSTRUCTION)
#define UT_RELAX_CPU() __asm__ __volatile__("rep; nop")
#elif defined _WIN32
/* In the Win32 API, the x86 PAUSE instruction is executed by calling
the YieldProcessor macro defined in WinNT.h. It is a CPU architecture-
independent way by using YieldProcessor. */
#define UT_RELAX_CPU() YieldProcessor()
#elif defined(__aarch64__)
/* A "yield" instruction in aarch64 is essentially a nop, and does not cause
enough delay to help backoff. "isb" is a barrier that, especially inside a
loop, creates a small delay without consuming ALU resources.
Experiments shown that adding the isb instruction improves stability and reduces
result jitter. Adding more delay to the UT_RELAX_CPU than a single isb reduces
performance. */
#define UT_RELAX_CPU() __asm__ __volatile__("isb" ::: "memory")
#else
#define UT_RELAX_CPU() __asm__ __volatile__("" ::: "memory")
#endif
 
#if defined(HAVE_HMT_PRIORITY_INSTRUCTION)
#define UT_LOW_PRIORITY_CPU() __asm__ __volatile__("or 1,1,1")
#define UT_RESUME_PRIORITY_CPU() __asm__ __volatile__("or 2,2,2")
#else
#define UT_LOW_PRIORITY_CPU() ((void)0)
#define UT_RESUME_PRIORITY_CPU() ((void)0)
#endif
 
#else                  /* !UNIV_HOTBACKUP */
#define UT_RELAX_CPU() /* No op */
#endif                 /* !UNIV_HOTBACKUP */
 
#ifndef UNIV_HOTBACKUP
 
/** Calculate the minimum of two pairs.
@param[out]     min_hi  MSB of the minimum pair
@param[out]     min_lo  LSB of the minimum pair
@param[in]      a_hi    MSB of the first pair
@param[in]      a_lo    LSB of the first pair
@param[in]      b_hi    MSB of the second pair
@param[in]      b_lo    LSB of the second pair */
static inline void ut_pair_min(ulint *min_hi, ulint *min_lo, ulint a_hi,
                               ulint a_lo, ulint b_hi, ulint b_lo);
#endif /* !UNIV_HOTBACKUP */
 
/** Compares two ulints.
@param[in]      a       ulint
@param[in]      b       ulint
@return 1 if a > b, 0 if a == b, -1 if a < b */
static inline int ut_ulint_cmp(ulint a, ulint b);
 
/** Compare two pairs of integers.
@param[in]      a_h     more significant part of first pair
@param[in]      a_l     less significant part of first pair
@param[in]      b_h     more significant part of second pair
@param[in]      b_l     less significant part of second pair
@return comparison result of (a_h,a_l) and (b_h,b_l)
@retval -1 if (a_h,a_l) is less than (b_h,b_l)
@retval 0 if (a_h,a_l) is equal to (b_h,b_l)
@retval 1 if (a_h,a_l) is greater than (b_h,b_l) */
[[nodiscard]] static inline int ut_pair_cmp(ulint a_h, ulint a_l, ulint b_h,
                                            ulint b_l);
 
/** Calculates fast the remainder of n/m when m is a power of two.
 @param n in: numerator
 @param m in: denominator, must be a power of two
 @return the remainder of n/m */
#define ut_2pow_remainder(n, m) ((n) & ((m)-1))
/** Calculates the biggest multiple of m that is not bigger than n
 when m is a power of two.  In other words, rounds n down to m * k.
 @param n in: number to round down
 @param m in: alignment, must be a power of two
 @return n rounded down to the biggest possible integer multiple of m */
#define ut_2pow_round(n, m) ((n) & ~((m)-1))
/** Align a number down to a multiple of a power of two.
@param n in: number to round down
@param m in: alignment, must be a power of two
@return n rounded down to the biggest possible integer multiple of m */
#define ut_calc_align_down(n, m) ut_2pow_round(n, m)
/** Calculates the smallest multiple of m that is not smaller than n
 when m is a power of two.  In other words, rounds n up to m * k.
 @param n in: number to round up
 @param m in: alignment, must be a power of two
 @return n rounded up to the smallest possible integer multiple of m */
#define ut_calc_align(n, m) (((n) + ((m)-1)) & ~((m)-1))
/** Calculates fast the 2-logarithm of a number, rounded upward to an
 integer.
 @return logarithm in the base 2, rounded upward */
constexpr ulint ut_2_log(ulint n); /*!< in: number */
 
/** Calculates 2 to power n.
@param[in]      n       power of 2
@return 2 to power n */
static inline uint32_t ut_2_exp(uint32_t n);
 
/** Calculates fast the number rounded up to the nearest power of 2.
@param[in]  n   number != 0
@return first power of 2 which is >= n */
ulint ut_2_power_up(ulint n);
 
/** Determine how many bytes (groups of 8 bits) are needed to
store the given number of bits.
@param b in: bits
@return number of bytes (octets) needed to represent b */
#define UT_BITS_IN_BYTES(b) (((b) + 7UL) / 8UL)
 
/** Determines if a number is zero or a power of two.
@param[in]      n       number
@return nonzero if n is zero or a power of two; zero otherwise */
#define ut_is_2pow(n) UNIV_LIKELY(!((n) & ((n)-1)))
 
/** Functor that compares two C strings. Can be used as a comparator for
e.g. std::map that uses char* as keys. */
struct ut_strcmp_functor {
  bool operator()(const char *a, const char *b) const {
    return (strcmp(a, b) < 0);
  }
};
 
namespace ut {
/** The current value of @@innodb_spin_wait_pause_multiplier. Determines
how many PAUSE instructions to emit for each requested unit of delay
when calling `ut_delay(delay)`. The default value of 50 causes `delay*50` PAUSES
which was equivalent to `delay` microseconds on 100 MHz Pentium + Visual C++.
Useful on processors which have "non-standard" duration of a single PAUSE
instruction - one can compensate for longer PAUSES by setting the
spin_wait_pause_multiplier to a smaller value on such machine */
extern ulong spin_wait_pause_multiplier;
}  // namespace ut
 
/** Runs an idle loop on CPU. The argument gives the desired delay
 in microseconds on 100 MHz Pentium + Visual C++.
 The actual duration depends on a product of `delay` and the current value of
 @@innodb_spin_wait_pause_multiplier.
 @param[in]   delay   delay in microseconds on 100 MHz Pentium, assuming
                      spin_wait_pause_multiplier is 50 (default).
 @return dummy value */
ulint ut_delay(ulint delay);
 
/* Forward declaration of transaction handle */
struct trx_t;
 
/** Get a fixed-length string, quoted as an SQL identifier.
If the string contains a slash '/', the string will be
output as two identifiers separated by a period (.),
as in SQL database_name.identifier.
 @param         [in]    trx             transaction (NULL=no quotes).
 @param         [in]    name            table name.
 @retval        String quoted as an SQL identifier.
*/
std::string ut_get_name(const trx_t *trx, const char *name);
 
/** Outputs a fixed-length string, quoted as an SQL identifier.
 If the string contains a slash '/', the string will be
 output as two identifiers separated by a period (.),
 as in SQL database_name.identifier. */
void ut_print_name(FILE *f,           /*!< in: output stream */
                   const trx_t *trx,  /*!< in: transaction */
                   const char *name); /*!< in: table name to print */
 
/** Format a table name, quoted as an SQL identifier.
If the name contains a slash '/', the result will contain two
identifiers separated by a period (.), as in SQL
database_name.table_name.
@see table_name_t
@param[in]      name            table or index name
@param[out]     formatted       formatted result, will be NUL-terminated
@param[in]      formatted_size  size of the buffer in bytes
@return pointer to 'formatted' */
char *ut_format_name(const char *name, char *formatted, ulint formatted_size);
 
/** Catenate files.
@param[in] dest Output file
@param[in] src Input file to be appended to output */
void ut_copy_file(FILE *dest, FILE *src);
 
/** Convert byte value to string with unit
@param[in]      data_bytes      byte value
@param[out]     data_str        formatted string */
void ut_format_byte_value(uint64_t data_bytes, std::string &data_str);
 
#ifdef _WIN32
/** A substitute for vsnprintf(3), formatted output conversion into
 a limited buffer. Note: this function DOES NOT return the number of
 characters that would have been printed if the buffer was unlimited because
 VC's _vsnprintf() returns -1 in this case and we would need to call
 _vscprintf() in addition to estimate that but we would need another copy
 of "ap" for that and VC does not provide va_copy(). */
void ut_vsnprintf(char *str,       /*!< out: string */
                  size_t size,     /*!< in: str size */
                  const char *fmt, /*!< in: format */
                  va_list ap);     /*!< in: format values */
#else
/** A wrapper for vsnprintf(3), formatted output conversion into
 a limited buffer. Note: this function DOES NOT return the number of
 characters that would have been printed if the buffer was unlimited because
 VC's _vsnprintf() returns -1 in this case and we would need to call
 _vscprintf() in addition to estimate that but we would need another copy
 of "ap" for that and VC does not provide va_copy(). */
#define ut_vsnprintf(buf, size, fmt, ap) ((void)vsnprintf(buf, size, fmt, ap))
#endif /* _WIN32 */
 
/** Convert an error number to a human readable text message. The
 returned string is static and should not be freed or modified.
 @return string, describing the error */
const char *ut_strerr(dberr_t num); /*!< in: error number */
 
namespace ib {
 
/** For measuring time elapsed. Since std::chrono::high_resolution_clock
may be influenced by a change in system time, it might not be steady.
So we use std::chrono::steady_clock for elapsed time. */
class Timer {
 public:
  using SC = std::chrono::steady_clock;
 
 public:
  /** Constructor. Starts/resets the timer to the current time. */
  Timer() noexcept { reset(); }
 
  /** Reset the timer to the current time. */
  void reset() { m_start = SC::now(); }
 
  /** @return the time elapsed in milliseconds. */
  template <typename T = std::chrono::milliseconds>
  int64_t elapsed() const noexcept {
    return std::chrono::duration_cast<T>(SC::now() - m_start).count();
  }
 
  /** Print time elapsed since last reset (in milliseconds) to the stream.
  @param[in,out] out  Stream to write to.
  @param[in] timer Timer to write to the stream.
  @return stream instance that was passed in. */
  template <typename T, typename Traits>
  friend std::basic_ostream<T, Traits> &operator<<(
      std::basic_ostream<T, Traits> &out, const Timer &timer) noexcept {
    return out << timer.elapsed();
  }
 
 private:
  /** High resolution timer instance used for timimg. */
  SC::time_point m_start;
};
 
}  // namespace ib
 
#ifdef UNIV_HOTBACKUP
/** Sprintfs a timestamp to a buffer with no spaces and with ':' characters
replaced by '_'.
@param[in]      buf     buffer where to sprintf */
void meb_sprintf_timestamp_without_extra_chars(char *buf);
#endif /* UNIV_HOTBACKUP */
 
struct Wait_stats {
  uint64_t wait_loops;
 
  explicit Wait_stats(uint64_t wait_loops = 0) : wait_loops(wait_loops) {}
 
  Wait_stats &operator+=(const Wait_stats &rhs) {
    wait_loops += rhs.wait_loops;
    return (*this);
  }
 
  Wait_stats operator+(const Wait_stats &rhs) const {
    return (Wait_stats{wait_loops + rhs.wait_loops});
  }
 
  bool any_waits() const { return (wait_loops != 0); }
};
 
namespace ib {
 
/** Allows to monitor an event processing times, allowing to throttle the
processing to one per throttle_delay_sec. */
class Throttler {
  using seconds = std::chrono::duration<uint64_t>;
  using clock = std::chrono::steady_clock;
  using time_point = std::chrono::time_point<clock, seconds>;
 
 public:
  explicit Throttler(seconds delay = seconds{10})
      : m_last_applied_time{}, m_throttle_delay{delay} {}
 
  /** Checks if the item should be processed or ignored to not process them more
  frequently than one per throttle_delay_sec. */
  bool apply() {
    const time_point current_time_in_sec =
        std::chrono::time_point_cast<seconds>(clock::now());
    auto last_apply_time = m_last_applied_time.load();
    if (last_apply_time + m_throttle_delay < current_time_in_sec) {
      if (m_last_applied_time.compare_exchange_strong(last_apply_time,
                                                      current_time_in_sec)) {
        return true;
      }
      /* Any race condition with other threads would mean someone just changed
      the `m_last_apply_time` and will print the message. We don't want
      to retry the operation again. */
    }
    return false;
  }
 
 private:
  /* Time when the last item was not throttled. Stored as number of seconds
  since epoch. */
  std::atomic<time_point> m_last_applied_time;
  static_assert(decltype(m_last_applied_time)::is_always_lock_free);
 
  /** Throttle all items within that amount seconds from the last non throttled
  one. */
  const seconds m_throttle_delay;
};
 
}  // namespace ib
 
namespace ut {
 
template <typename T, typename U>
constexpr bool can_type_fit_value(const U value) {
  return ((value > U(0)) == (T(value) > T(0))) && U(T(value)) == value;
}
template <typename T, typename U>
T clamp(U x) {
  return can_type_fit_value<T>(x) ? T(x)
         : x < 0                  ? std::numeric_limits<T>::min()
                                  : std::numeric_limits<T>::max();
}
 
}  // namespace ut
 
#include "ut0ut.ic"
 
#endif /* !ut0ut_h */