/*
* Copyright (c) 2020 Red Hat, Inc.
*
* 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; either version 2
* of the License, or (at your option) any later version.
*
* 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, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
* $Id: //eng/uds-releases/jasper/src/uds/cpu.h#1 $
*/
#ifndef CPU_H
#define CPU_H
#include "compiler.h"
#include "typeDefs.h"
/**
* The number of bytes in a CPU cache line. In the future, we'll probably need
* to move this to a processor-specific file or discover it at compilation
* time (or runtime, if sufficiently heterogeneous), but this will do for now.
* (Must be a \#define since enums are not proper compile-time constants.)
**/
#ifdef __PPC__
// N.B.: Some PPC processors have smaller cache lines.
#define CACHE_LINE_BYTES 128
#elif defined(__s390x__)
#define CACHE_LINE_BYTES 256
#elif defined(__x86_64__) || defined(__aarch64__)
#define CACHE_LINE_BYTES 64
#else
#error "unknown cache line size"
#endif
/**
* Minimize cache-miss latency by moving data into a CPU cache before it is
* accessed.
*
* @param address the address to fetch (may be invalid)
* @param forWrite must be constant at compile time--false if
* for reading, true if for writing
**/
static INLINE void prefetchAddress(const void *address, bool forWrite)
{
// forWrite won't won't be a constant if we are compiled with optimization
// turned off, in which case prefetching really doesn't matter.
if (__builtin_constant_p(forWrite)) {
__builtin_prefetch(address, forWrite);
}
}
/**
* Minimize cache-miss latency by moving a range of addresses into a
* CPU cache before they are accessed.
*
* @param start the starting address to fetch (may be invalid)
* @param size the number of bytes in the address range
* @param forWrite must be constant at compile time--false if
* for reading, true if for writing
**/
static INLINE void prefetchRange(const void *start,
unsigned int size,
bool forWrite)
{
// Count the number of cache lines to fetch, allowing for the address range
// to span an extra cache line boundary due to address alignment.
const char *address = (const char *) start;
unsigned int offset = ((uintptr_t) address % CACHE_LINE_BYTES);
size += offset;
unsigned int cacheLines = (1 + (size / CACHE_LINE_BYTES));
while (cacheLines-- > 0) {
prefetchAddress(address, forWrite);
address += CACHE_LINE_BYTES;
}
}
#endif /* CPU_H */