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/*****************************************************************************
Copyright (c) 2012, 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 "univ.i"
#include <string.h>
#include "os0thread.h"
/** CPU cache line size */
#ifndef UNIV_HOTBACKUP
# 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 */
#else
# define CACHE_LINE_SIZE 64
#endif /* UNIV_HOTBACKUP */
/** 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 */
size_t offset(size_t index) const UNIV_NOTHROW {
return(((index % N) + 1) * (CACHE_LINE_SIZE / sizeof(Type)));
}
};
#ifdef HAVE_SCHED_GETCPU
#include <utmpx.h>
/** Use the cpu id to index into the counter array. If it fails then
use the thread id. */
template <typename Type, int N>
struct get_sched_indexer_t : public generic_indexer_t<Type, N> {
/* @return result from sched_getcpu(), the thread id if it fails. */
size_t get_rnd_index() const UNIV_NOTHROW {
size_t cpu = sched_getcpu();
if (cpu == -1) {
cpu = (lint) os_thread_get_curr_id();
}
return(cpu);
}
};
#endif /* HAVE_SCHED_GETCPU */
/** Use the thread id to index into the counter array. */
template <typename Type, int N>
struct thread_id_indexer_t : public generic_indexer_t<Type, N> {
/* @return a random number, currently we use the thread id. Where
thread id is represented as a pointer, it may not work as
effectively. */
size_t get_rnd_index() const UNIV_NOTHROW {
return((lint) os_thread_get_curr_id());
}
/** @return a random offset to the array */
size_t get_rnd_offset() const UNIV_NOTHROW
{
return(generic_indexer_t<Type, N>::offset(get_rnd_index()));
}
};
/** 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 = thread_id_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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