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2008-10-06Merge branches 'x86/alternatives', 'x86/cleanups', 'x86/commandline', ↵Ingo Molnar
'x86/crashdump', 'x86/debug', 'x86/defconfig', 'x86/doc', 'x86/exports', 'x86/fpu', 'x86/gart', 'x86/idle', 'x86/mm', 'x86/mtrr', 'x86/nmi-watchdog', 'x86/oprofile', 'x86/paravirt', 'x86/reboot', 'x86/sparse-fixes', 'x86/tsc', 'x86/urgent' and 'x86/vmalloc' into x86-v28-for-linus-phase1
2008-09-06x86, tsc calibration: fixIngo Molnar
my brown paperbag day ... Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-04x86: quick TSC calibration, improveIngo Molnar
- make sure the final TSC timestamp is reliable too Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-04x86: quick TSC calibrationLinus Torvalds
Introduce a fast TSC-calibration method on sane hardware. It only uses 17920 PIT timer ticks to calibrate the TSC, plus 256 ticks on each side to make sure the TSC values were very close to the tick, so the whole calibration takes 15ms. Yet, despite only takign 15ms, we can actually give pretty stringent guarantees of accuracy: - the code requires that we hit each 256-counter block at least 50 times, so the TSC error is basically at *MOST* just a few PIT cycles off in any direction. In practice, it's going to be about one microseconds off (which is how long it takes to read the counter) - so over 17920 PIT cycles, we can pretty much guarantee that the calibration error is less than one half of a percent. My testing bears this out: on my machine, the quick-calibration reports 2934.085kHz, while the slow one reports 2933.415. Yes, the slower calibration is still more precise. For me, the slow calibration is stable to within about one hundreth of a percent, so it's (at a guess) roughly an order-and-a-half of magnitude more precise. The longer you wait, the more precise you can be. However, the nice thing about the fast TSC PIT synchronization is that it's pretty much _guaranteed_ to give that 0.5% precision, and fail gracefully (and very quickly) if it doesn't get it. And it really is fairly simple (even if there's a lot of _details_ there, and I didn't get all of those right ont he first try or even the second ;) The patch says "110 insertions", but 63 of those new lines are actually comments. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> --- arch/x86/kernel/tsc.c | 111 ++++++++++++++++++++++++++++++++++++++++++++++++- 1 files changed, 110 insertions(+), 1 deletions(-)
2008-09-04x86: TSC make the calibration loop smarterThomas Gleixner
The last changes made the calibration loop 250ms long which is far too much. Try to do that more clever. Experiments have shown that using a 10ms delay for the PIT based calibration gives us a good enough value. If we have a reference (HPET/PMTIMER) and the result of the PIT and the reference is close enough, then we can break out of the calibration loop on a match right away and use the reference value. Otherwise we just loop 3 times and decide then, which value to take. One caveat is that for virtualized environments the PIT calibration often does not work at all and I found out that 10us is a bit too short as well for the reference to give a sane result. The solution here is to make the last loop longer when the first two PIT calibrations failed. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-04x86: TSC: use one set of reference variablesThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-04x86: TSC: separate hpet/pmtimer calculation outThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-04x86: TSC: define the PIT latch value separateThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-03x86: Change warning message in TSC calibration.Alok N Kataria
When calibration against PIT fails, the warning that we print is misleading. In a virtualized environment the VM may get descheduled while calibration or, the check in PIT calibration may fail due to other virtualization overheads. The warning message explicitly assumes that calibration failed due to SMI's which may not be the case. Change that to something proper. Signed-off-by: Alok N Kataria <akataria@vmware.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-09-03Split up PIT part of TSC calibration from native_calibrate_tscLinus Torvalds
The TSC calibration function is still very complicated, but this makes it at least a little bit less so by moving the PIT part out into a helper function of its own. Tested-by: Larry Finger <Larry.Finger@lwfinger.net> Signed-of-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-09-02[x86] Fix TSC calibration issuesThomas Gleixner
Larry Finger reported at http://lkml.org/lkml/2008/9/1/90: An ancient laptop of mine started throwing errors from b43legacy when I started using 2.6.27 on it. This has been bisected to commit bfc0f59 "x86: merge tsc calibration". The unification of the TSC code adopted mostly the 64bit code, which prefers PMTIMER/HPET over the PIT calibration. Larrys system has an AMD K6 CPU. Such systems are known to have PMTIMER incarnations which run at double speed. This results in a miscalibration of the TSC by factor 0.5. So the resulting calibrated CPU/TSC speed is half of the real CPU speed, which means that the TSC based delay loop will run half the time it should run. That might explain why the b43legacy driver went berserk. On the other hand we know about systems, where the PIT based calibration results in random crap due to heavy SMI/SMM disturbance. On those systems the PMTIMER/HPET based calibration logic with SMI detection shows better results. According to Alok also virtualized systems suffer from the PIT calibration method. The solution is to use a more wreckage aware aproach than the current either/or decision. 1) reimplement the retry loop which was dropped from the 32bit code during the merge. It repeats the calibration and selects the lowest frequency value as this is probably the closest estimate to the real frequency 2) Monitor the delta of the TSC values in the delay loop which waits for the PIT counter to reach zero. If the maximum value is significantly different from the minimum, then we have a pretty safe indicator that the loop was disturbed by an SMI. 3) keep the pmtimer/hpet reference as a backup solution for systems where the SMI disturbance is a permanent point of failure for PIT based calibration 4) do the loop iteration for both methods, record the lowest value and decide after all iterations finished. 5) Set a clear preference to PIT based calibration when the result makes sense. The implementation does the reference calibration based on HPET/PMTIMER around the delay, which is necessary for the PIT anyway, but keeps separate TSC values to ensure the "independency" of the resulting calibration values. Tested on various 32bit/64bit machines including Geode 266Mhz, AMD K6 (affected machine with a double speed pmtimer which I grabbed out of the dump), Pentium class machines and AMD/Intel 64 bit boxen. Bisected-by: Larry Finger <Larry.Finger@lwfinger.net> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Larry Finger <Larry.Finger@lwfinger.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-08-25x86: fix cpufreq + sched_clock() regressionPeter Zijlstra
I noticed that my sched_clock() was slow on a number of machine, so I started looking at cpufreq. The below seems to fix the problem for me. Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-08-24x86: do not enable TSC notifier if we don't need itLinus Torvalds
Impact: crash on non-TSC-equipped CPUs Don't enable the TSC notifier if we *either*: 1. don't have a CPU, or 2. have a CPU with constant TSC. In either of those cases, the notifier is either damaging (1) or useless(2). From: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2008-08-18x86, tsc: fix section mismatch warningMarcin Slusarz
WARNING: vmlinux.o(.text+0x7950): Section mismatch in reference from the function native_calibrate_tsc() to the function .init.text:tsc_read_refs() The function native_calibrate_tsc() references the function __init tsc_read_refs(). This is often because native_calibrate_tsc lacks a __init annotation or the annotation of tsc_read_refs is wrong. tsc_read_refs is called from native_calibrate_tsc which is not __init and native_calibrate_tsc cannot be marked __init Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-15x86: fix TSC build error on 32bitThomas Gleixner
Dave Hansen reported a build error on 32bit which went unnoticed as newer gcc versions seem to optimize unused static functions away before compiling them. Make vread_tsc() depend on CONFIG_X86_64 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-07-10x86: remove duplicate call to use_tsc_delayGlauber Costa
Integration generated a duplicate call to use_tsc_delay. Particularly, the one that is done before we check for general tsc usability seems wrong. Signed-off-by: Glauber Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-09x86: provide delay loop for x86_64.Glauber Costa
This is for consistency with i386. We call use_tsc_delay() at tsc initialization for x86_64, so we'll be always using it. Signed-off-by: Glauber Costa <gcosta@redhat.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-09x86: rename paravirtualized TSC functionsAlok Kataria
Rename the paravirtualized calculate_cpu_khz to calibrate_tsc. In all cases, we actually calibrate_tsc and use that as the cpu_khz value. Signed-off-by: Alok N Kataria <akataria@vmware.com> Signed-off-by: Dan Hecht <dhecht@vmware.com> Cc: Dan Hecht <dhecht@vmware.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-09x86: merge tsc_init and clocksource codeAlok Kataria
Unify the clocksource code. Unify the tsc_init code. Signed-off-by: Alok N Kataria <akataria@vmware.com> Signed-off-by: Dan Hecht <dhecht@vmware.com> Cc: Dan Hecht <dhecht@vmware.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-09x86: merge the TSC cpu-freq codeAlok Kataria
Unify the TSC cpufreq code. Signed-off-by: Alok N Kataria <akataria@vmware.com> Signed-off-by: Dan Hecht <dhecht@vmware.com> Cc: Dan Hecht <dhecht@vmware.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-09x86: merge tsc calibrationAlok Kataria
Merge the tsc calibration code for the 32bit and 64bit kernel. The paravirtualized calculate_cpu_khz for 64bit now points to the correct tsc_calibrate code as in 32bit. Original native_calculate_cpu_khz for 64 bit is now called as calibrate_cpu. Also moved the recalibrate_cpu_khz function in the common file. Note that this function is called only from powernow K7 cpu freq driver. Signed-off-by: Alok N Kataria <akataria@vmware.com> Signed-off-by: Dan Hecht <dhecht@vmware.com> Cc: Dan Hecht <dhecht@vmware.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-09x86: merge sched_clock handlingAlok Kataria
Move the basic global variable definitions and sched_clock handling in the common "tsc.c" file. - Unify notsc kernel command line handling for 32 bit and 64bit. - Functional changes for 64bit. - "tsc_disabled" is updated if "notsc" is passed at boottime. - Fallback to jiffies for sched_clock, incase notsc is passed on commandline. Signed-off-by: Alok N Kataria <akataria@vmware.com> Signed-off-by: Dan Hecht <dhecht@vmware.com> Cc: Dan Hecht <dhecht@vmware.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>