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[librm] Add a profiling self-test for measuring mode transition times

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Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2014-05-02 15:20:56 +01:00
parent 9c16548506
commit bd640bc364
1 changed files with 77 additions and 0 deletions
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src/arch/i386/transitions/librm_test.c Normal file
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/*
* Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
*
* 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 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.
*/
FILE_LICENCE ( GPL2_OR_LATER );
/** @file
*
* Real mode transition self-tests
*
* This file allows for easy measurement of the time taken to perform
* real mode transitions, which may have a substantial overhead when
* running under a hypervisor.
*
*/
/* Forcibly enable assertions */
#undef NDEBUG
#include <ipxe/test.h>
#include <ipxe/profile.h>
#include <realmode.h>
/** Number of sample iterations for profiling */
#define PROFILE_COUNT 4096
/** Protected-to-real mode transition profiler */
static struct profiler p2r_profiler __profiler = { .name = "p2r" };
/** Real-to-protected mode transition profiler */
static struct profiler r2p_profiler __profiler = { .name = "r2p" };
/**
* Perform real mode transition self-tests
*
*/
static void librm_test_exec ( void ) {
unsigned int i;
unsigned long p2r_elapsed;
/* Profile mode transitions. We want to profile each
* direction of the transition separately, so perform an RDTSC
* while in real mode and tweak the profilers' start/stop
* times appropriately.
*/
for ( i = 0 ; i < PROFILE_COUNT ; i++ ) {
profile_start ( &p2r_profiler );
__asm__ __volatile__ ( REAL_CODE ( "rdtsc\n\t" )
: "=A" ( r2p_profiler.started ) : );
profile_stop ( &r2p_profiler );
p2r_elapsed = ( r2p_profiler.started - p2r_profiler.started );
profile_update ( &p2r_profiler, p2r_elapsed );
}
}
/** Real mode transition self-test */
struct self_test librm_test __self_test = {
.name = "librm",
.exec = librm_test_exec,
};
REQUIRE_OBJECT ( test );