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/* $Id: rdtsc.cpp $ */
/** @file
* rdtsc - Test if three consecutive rdtsc instructions return different values.
*/
/*
* Copyright (C) 2009-2023 Oracle and/or its affiliates.
*
* This file is part of VirtualBox base platform packages, as
* available from https://www.virtualbox.org.
*
* 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, in version 3 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, see <https://www.gnu.org/licenses>.
*
* The contents of this file may alternatively be used under the terms
* of the Common Development and Distribution License Version 1.0
* (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
* in the VirtualBox distribution, in which case the provisions of the
* CDDL are applicable instead of those of the GPL.
*
* You may elect to license modified versions of this file under the
* terms and conditions of either the GPL or the CDDL or both.
*
* SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
*/
/*********************************************************************************************************************************
* Header Files *
*********************************************************************************************************************************/
#include <iprt/errcore.h>
#include <iprt/initterm.h>
#include <iprt/message.h>
#include <iprt/stream.h>
#include <iprt/string.h>
#include <iprt/time.h>
/*********************************************************************************************************************************
* Structures and Typedefs *
*********************************************************************************************************************************/
typedef struct RDTSCRESULT
{
RTCCUINTREG uLow, uHigh;
} RDTSCRESULT;
/*********************************************************************************************************************************
* Global Variables *
*********************************************************************************************************************************/
extern "C" RDTSCRESULT g_aRdTscResults[]; /* rdtsc-asm.asm */
/*********************************************************************************************************************************
* Internal Functions *
*********************************************************************************************************************************/
/**
* Does 3 (32-bit) or 6 (64-bit) fast TSC reads and stores the result
* in g_aRdTscResults, starting with the 2nd entry.
*
* Starting the result storing at g_aRdTscResults[1] make it easy to do the
* comparisons in a loop.
*
* @returns Number of results read into g_aRdTscResults[1] and onwards.
*/
DECLASM(uint32_t) DoTscReads(void);
int main(int argc, char **argv)
{
int rc = RTR3InitExe(argc, &argv, 0);
if (RT_FAILURE(rc))
return RTMsgInitFailure(rc);
/*
* Tunables.
*/
uint64_t offJumpThreshold = _4G * 2;
unsigned cMaxLoops = 10000000;
unsigned cStatusEvery = 2000000;
unsigned cMinSeconds = 0;
for (int i = 1; i < argc; i++)
{
const char *psz = argv[i];
if (*psz == '-')
{
psz++;
char chOpt;
while ((chOpt = *psz++) != '\0')
{
/* Option value. */
const char *pszValue = NULL;
uint64_t uValue = 0;
switch (chOpt)
{
case 'l':
case 's':
case 'm':
if (*psz == '\0')
{
if (i + 1 >= argc)
return RTMsgSyntax("The %c option requires a value", chOpt);
pszValue = argv[++i];
}
else
pszValue = psz + (*psz == ':' || *psz == '=');
switch (chOpt)
{
case 'l':
case 's':
case 'm':
{
char *pszNext = NULL;
rc = RTStrToUInt64Ex(pszValue, &pszNext, 0, &uValue);
if (RT_FAILURE(rc))
return RTMsgSyntax("Bad number: %s (%Rrc)", pszValue, rc);
if (pszNext && *pszNext != '\0')
{
if (*pszNext == 'M'&& pszNext[1] == '\0')
uValue *= _1M;
else if (*pszNext == 'K' && pszNext[1] == '\0')
uValue *= _1K;
else if (*pszNext == 'G' && pszNext[1] == '\0')
uValue *= _1G;
else
return RTMsgSyntax("Bad value format for option %c: %s", chOpt, pszValue);
}
break;
}
}
break;
}
/* handle the option. */
switch (chOpt)
{
case 'l':
cMaxLoops = uValue;
break;
case 'm':
cMinSeconds = uValue;
break;
case 's':
cStatusEvery = uValue;
break;
case 'h':
case '?':
RTPrintf("usage: rdtsc [-l <loops>] [-s <loops-between-status>]\n"
" [-m <minimum-seconds-to-run>]\n");
return RTEXITCODE_SUCCESS;
default:
return RTMsgSyntax("Unknown option %c (argument %d)\n", chOpt, i);
}
}
}
else
return RTMsgSyntax("argument %d (%s): not an option\n", i, psz);
}
/*
* Do the job.
*/
uint64_t const nsTsStart = RTTimeNanoTS();
unsigned cOuterLoops = 0;
unsigned cLoopsToNextStatus = cStatusEvery;
unsigned cRdTscInstructions = 0;
unsigned cBackwards = 0;
unsigned cSame = 0;
unsigned cBadValues = 0;
unsigned cJumps = 0;
uint64_t offMaxJump = 0;
uint64_t offMinIncr = UINT64_MAX;
uint64_t offMaxIncr = 0;
g_aRdTscResults[0] = g_aRdTscResults[DoTscReads() - 1];
for (;;)
{
for (unsigned iLoop = 0; iLoop < cMaxLoops; iLoop++)
{
uint32_t const cResults = DoTscReads();
cRdTscInstructions += cResults;
for (uint32_t i = 0; i < cResults; i++)
{
uint64_t uPrev = RT_MAKE_U64((uint32_t)g_aRdTscResults[i ].uLow, (uint32_t)g_aRdTscResults[i ].uHigh);
uint64_t uCur = RT_MAKE_U64((uint32_t)g_aRdTscResults[i + 1].uLow, (uint32_t)g_aRdTscResults[i + 1].uHigh);
if (RT_LIKELY(uCur != uPrev))
{
int64_t offDelta = uCur - uPrev;
if (RT_LIKELY(offDelta >= 0))
{
if (RT_LIKELY((uint64_t)offDelta < offJumpThreshold))
{
if ((uint64_t)offDelta < offMinIncr)
offMinIncr = offDelta;
if ((uint64_t)offDelta > offMaxIncr && i != 0)
offMaxIncr = offDelta;
}
else
{
cJumps++;
if ((uint64_t)offDelta > offMaxJump)
offMaxJump = offDelta;
RTPrintf("%u/%u: Jump: %#010x`%08x -> %#010x`%08x\n", cOuterLoops, iLoop,
(unsigned)g_aRdTscResults[i].uHigh, (unsigned)g_aRdTscResults[i].uLow,
(unsigned)g_aRdTscResults[i + 1].uHigh, (unsigned)g_aRdTscResults[i + 1].uLow);
}
}
else
{
cBackwards++;
RTPrintf("%u/%u: Back: %#010x`%08x -> %#010x`%08x\n", cOuterLoops, iLoop,
(unsigned)g_aRdTscResults[i].uHigh, (unsigned)g_aRdTscResults[i].uLow,
(unsigned)g_aRdTscResults[i + 1].uHigh, (unsigned)g_aRdTscResults[i + 1].uLow);
}
}
else
{
cSame++;
RTPrintf("%u/%u: Same: %#010x`%08x -> %#010x`%08x\n", cOuterLoops, iLoop,
(unsigned)g_aRdTscResults[i].uHigh, (unsigned)g_aRdTscResults[i].uLow,
(unsigned)g_aRdTscResults[i + 1].uHigh, (unsigned)g_aRdTscResults[i + 1].uLow);
}
#if ARCH_BITS == 64
if ((g_aRdTscResults[i + 1].uLow >> 32) || (g_aRdTscResults[i + 1].uHigh >> 32))
cBadValues++;
#endif
}
/* Copy the last value for the next iteration. */
g_aRdTscResults[0] = g_aRdTscResults[cResults];
/* Display status. */
if (RT_LIKELY(--cLoopsToNextStatus > 0))
{ /* likely */ }
else
{
cLoopsToNextStatus = cStatusEvery;
RTPrintf("%u/%u: %#010x`%08x\n", cOuterLoops, iLoop,
(unsigned)g_aRdTscResults[cResults].uHigh, (unsigned)g_aRdTscResults[cResults].uLow);
}
}
/*
* Check minimum number of seconds.
*/
cOuterLoops++;
if (!cMinSeconds)
break;
uint64_t nsElapsed = RTTimeNanoTS() - nsTsStart;
if (nsElapsed >= cMinSeconds * RT_NS_1SEC_64)
break;
}
/*
* Summary.
*/
if (cBackwards == 0 && cSame == 0 && cJumps == 0 && cBadValues == 0)
{
RTPrintf("rdtsc: Success (%u RDTSC over %u*%u loops, deltas: %#x`%08x..%#x`%08x)\n",
cRdTscInstructions, cOuterLoops, cMaxLoops,
(unsigned)(offMinIncr >> 32), (unsigned)offMinIncr, (unsigned)(offMaxIncr >> 32), (unsigned)offMaxIncr);
return RTEXITCODE_SUCCESS;
}
RTPrintf("RDTSC instructions: %u\n", cRdTscInstructions);
RTPrintf("Loops: %u * %u => %u\n", cMaxLoops, cOuterLoops, cOuterLoops * cMaxLoops);
RTPrintf("Backwards: %u\n", cBackwards);
RTPrintf("Jumps: %u\n", cJumps);
RTPrintf("Max jumps: %#010x`%08x\n", (unsigned)(offMaxJump >> 32), (unsigned)offMaxJump);
RTPrintf("Same value: %u\n", cSame);
RTPrintf("Bad values: %u\n", cBadValues);
RTPrintf("Min increment: %#010x`%08x\n", (unsigned)(offMinIncr >> 32), (unsigned)offMinIncr);
RTPrintf("Max increment: %#010x`%08x\n", (unsigned)(offMaxIncr >> 32), (unsigned)offMaxIncr);
return RTEXITCODE_FAILURE;
}
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