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/*
Copyright (c) 2012, Oracle and/or its affiliates. All Rights Reserved.
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 <string.h>
/** CPU cache line size */
#define UT_CACHE_LINE_SIZE 64
/** Default number of slots to use in ib_counter_t */
#define IB_N_SLOTS 64
#ifdef _WIN32
#define get_curr_thread_id() GetCurrentThreadId()
#else
#define get_curr_thread_id() pthread_self()
#endif
#define UT_ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
/** Get the offset into the counter array. */
template <typename Type, int N>
struct generic_indexer_t {
/** Default constructor/destructor should be OK. */
/** @return offset within m_counter */
size_t offset(size_t index) const {
return(((index % N) + 1) * (UT_CACHE_LINE_SIZE / sizeof(Type)));
}
};
#ifdef HAVE_SCHED_GETCPU
//#include <utmpx.h> // Including this causes problems with EMPTY symbol
#include <sched.h> // Include this instead
/** 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> {
/** Default constructor/destructor should be OK. */
/* @return result from sched_getcpu(), the thread id if it fails. */
size_t get_rnd_index() const {
size_t cpu = sched_getcpu();
if (cpu == (size_t) -1) {
cpu = (size_t) get_curr_thread_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> {
/** Default constructor/destructor should are OK. */
/* @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 {
return (size_t)get_curr_thread_id();
}
};
/** For counters wher N=1 */
template <typename Type, int N=1>
struct single_indexer_t {
/** Default constructor/destructor should are OK. */
/** @return offset within m_counter */
size_t offset(size_t index) const {
DBUG_ASSERT(N == 1);
return((UT_CACHE_LINE_SIZE / sizeof(Type)));
}
/* @return 1 */
size_t get_rnd_index() const {
DBUG_ASSERT(N == 1);
return(1);
}
};
/** 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
UT_CACHE_LINE_SIZE bytes */
template <
typename Type,
int N = IB_N_SLOTS,
template<typename, int> class Indexer = thread_id_indexer_t>
class ib_counter_t {
public:
ib_counter_t() { memset(m_counter, 0x0, sizeof(m_counter)); }
~ib_counter_t()
{
DBUG_ASSERT(validate());
}
bool validate() {
#ifdef UNIV_DEBUG
size_t n = (UT_CACHE_LINE_SIZE / sizeof(Type));
/* Check that we aren't writing outside our defined bounds. */
for (size_t i = 0; i < UT_ARRAY_SIZE(m_counter); i += n) {
for (size_t j = 1; j < n - 1; ++j) {
DBUG_ASSERT(m_counter[i + j] == 0);
}
}
#endif /* UNIV_DEBUG */
return(true);
}
/** If you can't use a good index id. Increment by 1. */
void inc() { add(1); }
/** If you can't use a good index id.
* @param n - is the amount to increment */
void add(Type n) {
size_t i = m_policy.offset(m_policy.get_rnd_index());
DBUG_ASSERT(i < UT_ARRAY_SIZE(m_counter));
m_counter[i] += n;
}
/** Use this if you can use a unique indentifier, saves a
call to get_rnd_index().
@param i - index into a slot
@param n - amount to increment */
void add(size_t index, Type n) {
size_t i = m_policy.offset(index);
DBUG_ASSERT(i < UT_ARRAY_SIZE(m_counter));
m_counter[i] += n;
}
/** If you can't use a good index id. Decrement by 1. */
void dec() { sub(1); }
/** If you can't use a good index id.
* @param - n is the amount to decrement */
void sub(Type n) {
size_t i = m_policy.offset(m_policy.get_rnd_index());
DBUG_ASSERT(i < UT_ARRAY_SIZE(m_counter));
m_counter[i] -= n;
}
/** Use this if you can use a unique indentifier, saves a
call to get_rnd_index().
@param i - index into a slot
@param n - amount to decrement */
void sub(size_t index, Type n) {
size_t i = m_policy.offset(index);
DBUG_ASSERT(i < UT_ARRAY_SIZE(m_counter));
m_counter[i] -= n;
}
/* @return total value - not 100% accurate, since it is not atomic. */
operator Type() const {
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) * (UT_CACHE_LINE_SIZE / sizeof(Type))];
};
#endif /* UT0COUNTER_H */
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