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/*****************************************************************************
Copyright (c) 2012, 2015, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2017, MariaDB Corporation.
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA
*****************************************************************************/
/**************************************************//**
@file include/ut0counter.h
Counter utility class
Created 2012/04/12 by Sunny Bains
*******************************************************/
#ifndef ut0counter_h
#define ut0counter_h
#include <my_rdtsc.h>
#include "univ.i"
#include "os0thread.h"
/** CPU cache line size */
#ifdef CPU_LEVEL1_DCACHE_LINESIZE
# define CACHE_LINE_SIZE CPU_LEVEL1_DCACHE_LINESIZE
#else
# error CPU_LEVEL1_DCACHE_LINESIZE is undefined
#endif /* CPU_LEVEL1_DCACHE_LINESIZE */
/** Default number of slots to use in ib_counter_t */
#define IB_N_SLOTS 64
/** Get the offset into the counter array. */
template <typename Type, int N>
struct generic_indexer_t {
/** @return offset within m_counter */
static size_t offset(size_t index) UNIV_NOTHROW
{
return(((index % N) + 1) * (CACHE_LINE_SIZE / sizeof(Type)));
}
};
/** Use the result of my_timer_cycles(), which mainly uses RDTSC for cycles,
to index into the counter array. See the comments for my_timer_cycles() */
template <typename Type=ulint, int N=1>
struct counter_indexer_t : public generic_indexer_t<Type, N> {
/** @return result from RDTSC or similar functions. */
static size_t get_rnd_index() UNIV_NOTHROW
{
size_t c = static_cast<size_t>(my_timer_cycles());
if (c != 0) {
return(c);
} else {
/* We may go here if my_timer_cycles() returns 0,
so we have to have the plan B for the counter. */
#if !defined(_WIN32)
return(size_t(os_thread_get_curr_id()));
#else
LARGE_INTEGER cnt;
QueryPerformanceCounter(&cnt);
return(static_cast<size_t>(cnt.QuadPart));
#endif /* !_WIN32 */
}
}
/** @return a random offset to the array */
static size_t get_rnd_offset() UNIV_NOTHROW
{
return(generic_indexer_t<Type, N>::offset(get_rnd_index()));
}
};
#define default_indexer_t counter_indexer_t
/** Class for using fuzzy counters. The counter is not protected by any
mutex and the results are not guaranteed to be 100% accurate but close
enough. Creates an array of counters and separates each element by the
CACHE_LINE_SIZE bytes */
template <
typename Type,
int N = IB_N_SLOTS,
template<typename, int> class Indexer = default_indexer_t>
struct MY_ALIGNED(CACHE_LINE_SIZE) ib_counter_t
{
#ifdef UNIV_DEBUG
~ib_counter_t()
{
size_t n = (CACHE_LINE_SIZE / sizeof(Type));
/* Check that we aren't writing outside our defined bounds. */
for (size_t i = 0; i < UT_ARR_SIZE(m_counter); i += n) {
for (size_t j = 1; j < n - 1; ++j) {
ut_ad(m_counter[i + j] == 0);
}
}
}
#endif /* UNIV_DEBUG */
/** Increment the counter by 1. */
void inc() UNIV_NOTHROW { add(1); }
/** Increment the counter by 1.
@param[in] index a reasonably thread-unique identifier */
void inc(size_t index) UNIV_NOTHROW { add(index, 1); }
/** Add to the counter.
@param[in] n amount to be added */
void add(Type n) UNIV_NOTHROW { add(m_policy.get_rnd_offset(), n); }
/** Add to the counter.
@param[in] index a reasonably thread-unique identifier
@param[in] n amount to be added */
void add(size_t index, Type n) UNIV_NOTHROW {
size_t i = m_policy.offset(index);
ut_ad(i < UT_ARR_SIZE(m_counter));
m_counter[i] += n;
}
/* @return total value - not 100% accurate, since it is not atomic. */
operator Type() const UNIV_NOTHROW {
Type total = 0;
for (size_t i = 0; i < N; ++i) {
total += m_counter[m_policy.offset(i)];
}
return(total);
}
private:
/** Indexer into the array */
Indexer<Type, N>m_policy;
/** Slot 0 is unused. */
Type m_counter[(N + 1) * (CACHE_LINE_SIZE / sizeof(Type))];
};
#endif /* ut0counter_h */
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