path: root/init/calibrate.c
AgeCommit message (Collapse)Author
2012-03-23init: check printed flag to skip printing messageDiwakar Tundlam
Otherwise the 'Calibration skipped' message gets printed everytime a CPU is hotplugged in, cluttering console for systems that frequently hotplug CPUs. Signed-off-by: Diwakar Tundlam <dtundlam@nvidia.com> Cc: Phil Carmody <ext-phil.2.carmody@nokia.com> Cc: Russell King <rmk+kernel@arm.linux.org.uk> Cc: Greg KH <greg@kroah.com> Cc: Sameer Nanda <snanda@chromium.org> Cc: Peter De Schrijver <pdeschrijver@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-12-05x86: Reduce clock calibration time during slave cpu startupJack Steiner
Reduce the startup time for slave cpus. Adds hooks for an arch-specific function for clock calibration. These hooks are used on x86. If a newly started cpu has the same phys_proc_id as a core already active, uses the TSC for the delay loop and has a CONSTANT_TSC, use the already-calculated value of loops_per_jiffy. This patch reduces the time required to start slave cpus on a 4096 cpu system from: 465 sec OLD 62 sec NEW This reduces boot time on a 4096p system by almost 7 minutes. Nice... Signed-off-by: Jack Steiner <steiner@sgi.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: John Stultz <john.stultz@linaro.org> [fix CONFIG_SMP=n build] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-07-25init: skip calibration delay if previously doneSameer Nanda
For each CPU, do the calibration delay only once. For subsequent calls, use the cached per-CPU value of loops_per_jiffy. This saves about 200ms of resume time on dual core Intel Atom N5xx based systems. This helps bring down the kernel resume time on such systems from about 500ms to about 300ms. [akpm@linux-foundation.org: make cpu_loops_per_jiffy static] [akpm@linux-foundation.org: clean up message text] [akpm@linux-foundation.org: fix things up after upstream rmk changes] Signed-off-by: Sameer Nanda <snanda@chromium.org> Cc: Phil Carmody <ext-phil.2.carmody@nokia.com> Cc: Andrew Worsley <amworsley@gmail.com> Cc: David Daney <ddaney@caviumnetworks.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-06-23Fix CPU spinlock lockups on secondary CPU bringupRussell King
Secondary CPU bringup typically calls calibrate_delay() during its initialization. However, calibrate_delay() modifies a global variable (loops_per_jiffy) used for udelay() and __delay(). A side effect of 71c696b1 ("calibrate: extract fall-back calculation into own helper") introduced in the 2.6.39 merge window means that we end up with a substantial period where loops_per_jiffy is zero. This causes the spinlock debugging code to malfunction: u64 loops = loops_per_jiffy * HZ; for (;;) { for (i = 0; i < loops; i++) { if (arch_spin_trylock(&lock->raw_lock)) return; __delay(1); } ... } by never calling arch_spin_trylock() - resulting in the CPU locking up in an infinite loop inside __spin_lock_debug(). Work around this by only writing to loops_per_jiffy only once we have completed all the calibration decisions. Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Cc: <stable@kernel.org> (2.6.39-stable) -- Better solutions (such as omitting the calibration for secondary CPUs, or arranging for calibrate_delay() to return the LPJ value and leave it to the caller to decide where to store it) are a possibility, but would be much more invasive into each architecture. I think this is the best solution for -rc and stable, but it should be revisited for the next merge window. init/calibrate.c | 14 ++++++++------ 1 files changed, 8 insertions(+), 6 deletions(-) Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-06-15init/calibrate.c: remove annoying printkBorislav Petkov
Remove calibrate_delay_direct()'s KERN_DEBUG printk related to bogomips calculation as it appears when booting every core on setups with 'ignore_loglevel' which dmesg people scan for possible issues. As the message doesn't show very useful information to the widest audience of kernel boot message gazers, it should be removed. Introduced by commit d2b463135f84 ("init/calibrate.c: fix for critical bogoMIPS intermittent calculation failure"). Signed-off-by: Borislav Petkov <borislav.petkov@amd.com> Cc: Andrew Worsley <amworsley@gmail.com> Cc: Phil Carmody <ext-phil.2.carmody@nokia.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-05-25init/calibrate.c: fix for critical bogoMIPS intermittent calculation failureAndrew Worsley
A fix to the TSC (Time Stamp Counter) based bogoMIPS calculation used on secondary CPUs which has two faults: 1: Not handling wrapping of the lower 32 bits of the TSC counter on 32bit kernel - perhaps TSC is not reset by a warm reset? 2: TSC and Jiffies are no incrementing together properly. Either jiffies increment too quickly or Time Stamp Counter isn't incremented in during an SMI but the real time clock is and jiffies are incremented. Case 1 can result in a factor of 16 too large a value which makes udelay() values too small and can cause mysterious driver errors. Case 2 appears to give smaller 10-15% errors after averaging but enough to cause occasional failures on my own board I have tested this code on my own branch and attach patch suitable for current kernel code. See below for examples of the failures and how the fix handles these situations now. I reported this issue earlier here: Intermittent problem with BogoMIPs calculation on Intel AP CPUs - http://marc.info/?l=linux-kernel&m=129947246316875&w=4 I suspect this issue has been seen by others but as it is intermittent and bogoMIPS for secondary CPUs are no longer printed out it might have been difficult to identify this as the cause. Perhaps these unresolved issues, although quite old, might be relevant as possibly this fault has been around for a while. In particular Case 1 may only be relevant to 32bit kernels on newer HW (most people run 64bit kernels?). Case 2 is less dramatic since the earlier fix in this area and also intermittent. Re: bogomips discrepancy on Intel Core2 Quad CPU - http://marc.info/?l=linux-kernel&m=118929277524298&w=4 slow system and bogus bogomips - http://marc.info/?l=linux-kernel&m=116791286716107&w=4 Re: Re: [RFC-PATCH] clocksource: update lpj if clocksource has - http://marc.info/?l=linux-kernel&m=128952775819467&w=4 This issue is masked a little by commit feae3203d711db0a ("timers, init: Limit the number of per cpu calibration bootup messages") which only prints out the first bogoMIPS value making it much harder to notice other values differing. Perhaps it should be changed to only suppress them when they are similar values? Here are some outputs showing faults occurring and the new code handling them properly. See my earlier message for examples of the original failure. Case 1: A Time Stamp Counter wrap: ... Calibrating delay loop (skipped), value calculated using timer frequency.. 6332.70 BogoMIPS (lpj=31663540) .... calibrate_delay_direct() timer_rate_max=31666493 timer_rate_min=31666151 pre_start=4170369255 pre_end=4202035539 calibrate_delay_direct() timer_rate_max=2425955274 timer_rate_min=2425954941 pre_start=4265368533 pre_end=2396356387 calibrate_delay_direct() ignoring timer_rate as we had a TSC wrap around start=4265368581 >=post_end=2396356511 calibrate_delay_direct() timer_rate_max=31666274 timer_rate_min=31665942 pre_start=2440373374 pre_end=2472039515 calibrate_delay_direct() timer_rate_max=31666492 timer_rate_min=31666160 pre_start=2535372139 pre_end=2567038422 calibrate_delay_direct() timer_rate_max=31666455 timer_rate_min=31666207 pre_start=2630371084 pre_end=2662037415 Calibrating delay using timer specific routine.. 6333.28 BogoMIPS (lpj=31666428) Total of 2 processors activated (12665.99 BogoMIPS). .... Case 2: Some thing (presumably the SMM interrupt?) causing the very low increase in TSC counter for the DELAY_CALIBRATION_TICKS increase in jiffies ... Calibrating delay loop (skipped), value calculated using timer frequency.. 6333.25 BogoMIPS (lpj=31666270) ... calibrate_delay_direct() timer_rate_max=31666483 timer_rate_min=31666074 pre_start=4199536526 pre_end=4231202809 calibrate_delay_direct() timer_rate_max=864348 timer_rate_min=864016 pre_start=2405343672 pre_end=2406207897 calibrate_delay_direct() timer_rate_max=31666483 timer_rate_min=31666179 pre_start=2469540464 pre_end=2501206823 calibrate_delay_direct() timer_rate_max=31666511 timer_rate_min=31666122 pre_start=2564539400 pre_end=2596205712 calibrate_delay_direct() timer_rate_max=31666084 timer_rate_min=31665685 pre_start=2659538782 pre_end=2691204657 calibrate_delay_direct() dropping min bogoMips estimate 1 = 864348 Calibrating delay using timer specific routine.. 6333.27 BogoMIPS (lpj=31666390) Total of 2 processors activated (12666.53 BogoMIPS). ... After 70 boots I saw 2 variations <1% slip through [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: fix straggly printk mess] Signed-off-by: Andrew Worsley <amworsley@gmail.com> Reviewed-by: Phil Carmody <ext-phil.2.carmody@nokia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22calibrate: retry with wider bounds when converge seems to failPhil Carmody
Systems with unmaskable interrupts such as SMIs may massively underestimate loops_per_jiffy, and fail to converge anywhere near the real value. A case seen on x86_64 was an initial estimate of 256<<12, which converged to 511<<12 where the real value should have been over 630<<12. This admitedly requires bypassing the TSC calibration (lpj_fine), and a failure to settle in the direct calibration too, but is physically possible. This failure does not depend on my previous calibration optimisation, but by luck is easy to fix with the optimisation in place with a trivial retry loop. In the context of the optimised converging method, as we can no longer trust the starting estimate, enlarge the search bounds exponentially so that the number of retries is logarithmically bounded. [akpm@linux-foundation.org: mention x86_64 SMIs in comment] Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Tested-by: Stephen Boyd <sboyd@codeaurora.org> Cc: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22calibrate: home in on correct lpj value more quicklyPhil Carmody
Binary chop with a jiffy-resync on each step to find an upper bound is slow, so just race in a tight-ish loop to find an underestimate. If done with lots of individual steps, sometimes several hundreds of iterations would be required, which would impose a significant overhead, and make the initial estimate very low. By taking slowly increasing steps there will be less overhead. E.g. an x86_64 2.67GHz could have fitted in 613 individual small delays, but in reality should have been able to fit in a single delay 644 times longer, so underestimated by 31 steps. To reach the equivalent of 644 small delays with the accelerating scheme now requires about 130 iterations, so has <1/4th of the overhead, and can therefore be expected to underestimate by only 7 steps. As now we have a better initial estimate we can binary chop over a smaller range. With the loop overhead in the initial estimate kept low, and the step sizes moderate, we won't have under-estimated by much, so chose as tight a range as we can. Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Tested-by: Stephen Boyd <sboyd@codeaurora.org> Cc: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22calibrate: extract fall-back calculation into own helperPhil Carmody
The motivation for this patch series is that currently our OMAP calibrates itself using the trial-and-error binary chop fallback that some other architectures no longer need to perform. This is a lengthy process, taking 0.2s in an environment where boot time is of great interest. Patch 2/4 has two optimisations. Firstly, it replaces the initial repeated- doubling to find the relevant power of 2 with a tight loop that just does as much as it can in a jiffy. Secondly, it doesn't binary chop over an entire power of 2 range, it choses a much smaller range based on how much it squeezed in, and failed to squeeze in, during the first stage. Both are significant optimisations, and bring our calibration down from 23 jiffies to 5, and, in the process, often arrive at a more accurate lpj value. The 'bands' and 'sub-logarithmic' growth may look over-engineered, but they only cost a small level of inaccuracy in the initial guess (for all architectures) in order to avoid the very large inaccuracies that appeared during testing (on x86_64 architectures, and presumably others with less metronomic operation). Note that due to the existence of the TSC and other timers, the x86_64 will not typically use this fallback routine, but I wanted to code defensively, able to cope with all kinds of processor behaviours and kernel command line options. Patch 3/4 is an additional trap for the nightmare scenario where the initial estimate is very inaccurate, possibly due to things like SMIs. It simply retries with a larger bound. Stephen said: I tried this patch set out on an MSM7630. : : Before: : : Calibrating delay loop... 681.57 BogoMIPS (lpj=3407872) : : After: : : Calibrating delay loop... 680.75 BogoMIPS (lpj=3403776) : : But the really good news is calibration time dropped from ~247ms to ~56ms. : Sadly we won't be able to benefit from this should my udelay patches make : it into ARM because we would be using calibrate_delay_direct() instead (at : least on machines who choose to). Can we somehow reapply the logic behind : this to calibrate_delay_direct()? That would be even better, but this is : definitely a boot time improvement. : : Or maybe we could just replace calibrate_delay_direct() with this fallback : calculation? If __delay() is a thin wrapper around read_current_timer() : it should work just as well (plus patch 3 makes it handle SMIs). I'll try : that out. This patch: ... so that it can be modified more clinically. This is almost entirely cosmetic. The only change to the operation is that the global variable is only set once after the estimation is completed, rather than taking on all the intermediate values. However, there are no readers of that variable, so this change is unimportant. Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Tested-by: Stephen Boyd <sboyd@codeaurora.org> Cc: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-02-10fix jiffy calculations in calibrate_delay_direct to handle overflowTim Deegan
Fixes a hang when booting as dom0 under Xen, when jiffies can be quite large by the time the kernel init gets this far. Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com> [jbeulich@novell.com: !time_after() -> time_before_eq() as suggested by Jiri Slaby] Signed-off-by: Jan Beulich <jbeulich@novell.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-11-26timers, init: Limit the number of per cpu calibration bootup messagesMike Travis
Limit the number of per cpu calibration messages by only printing out results for the first cpu to boot. Also, don't print "CPUx is down" as this is expected, and we don't need 4096 reminders... ;-) Signed-off-by: Mike Travis <travis@sgi.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Roland Dreier <rdreier@cisco.com> Cc: Randy Dunlap <rdunlap@xenotime.net> Cc: Tejun Heo <tj@kernel.org> Cc: Andi Kleen <andi@firstfloor.org> Cc: Greg Kroah-Hartman <gregkh@suse.de> Cc: Yinghai Lu <yhlu.kernel@gmail.com> Cc: David Rientjes <rientjes@google.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Cc: Jack Steiner <steiner@sgi.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <20091118002219.889552000@alcatraz.americas.sgi.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-28x86: remove stray <6> in BogoMIPS printkJoe Perches
Rabin Vincent noticed that there's a stray <6> in BogoMIPS printk: > Remove the extra KERN_INFO which causes this: > Calibrating delay loop... <6>179.40 BogoMIPS (lpj=897024) > - printk(KERN_INFO "%lu.%02lu BogoMIPS (lpj=%lu)\n", > - loops_per_jiffy/(500000/HZ), > - (loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy); > + printk("%lu.%02lu BogoMIPS (lpj=%lu)\n", > + loops_per_jiffy/(500000/HZ), > + (loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy); > } How about just using KERN_CONT and leaving the whitespace for a patch that does the entire file? Reported-by: Rabin Vincent <rabin@rab.in>
2008-06-24x86: use cpu_khz for loops_per_jiffy calculation, cleanupAlok Kataria
As suggested by Ingo, remove all references to tsc from init/calibrate.c TSC is x86 specific, and using tsc in variable names in a generic file should be avoided. lpj_tsc is now called lpj_fine, since it is related to fine tuning of lpj value. Also tsc_rate_* is called timer_rate_* Signed-off-by: Alok N Kataria <akataria@vmware.com> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Daniel Hecht <dhecht@vmware.com> Cc: Tim Mann <mann@vmware.com> Cc: Zach Amsden <zach@vmware.com> Cc: Sahil Rihan <srihan@vmware.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-23x86: use cpu_khz for loops_per_jiffy calculationAlok Kataria
On the x86 platform we can use the value of tsc_khz computed during tsc calibration to calculate the loops_per_jiffy value. Its very important to keep the error in lpj values to minimum as any error in that may result in kernel panic in check_timer. In virtualization environment, On a highly overloaded host the guest delay calibration may sometimes result in errors beyond the ~50% that timer_irq_works can handle, resulting in the guest panicking. Does some formating changes to lpj_setup code to now have a single printk to print the bogomips value. We do this only for the boot processor because the AP's can have different base frequencies or the BIOS might boot a AP at a different frequency. Signed-off-by: Alok N Kataria <akataria@vmware.com> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Daniel Hecht <dhecht@vmware.com> Cc: Tim Mann <mann@vmware.com> Cc: Zach Amsden <zach@vmware.com> Cc: Sahil Rihan <srihan@vmware.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-02-06calibrate_delay() must be __cpuinitAdrian Bunk
calibrate_delay() must be __cpuinit, not __{dev,}init. I've verified that this is correct for all users. While doing the latter, I also did the following cleanups: - remove pointless additional prototypes in C files - ensure all users #include <linux/delay.h> This fixes the following section mismatches with CONFIG_HOTPLUG=n, CONFIG_HOTPLUG_CPU=y: WARNING: vmlinux.o(.text+0x1128d): Section mismatch: reference to .init.text.1:calibrate_delay (between 'check_cx686_slop' and 'set_cx86_reorder') WARNING: vmlinux.o(.text+0x25102): Section mismatch: reference to .init.text.1:calibrate_delay (between 'smp_callin' and 'cpu_coregroup_map') Signed-off-by: Adrian Bunk <bunk@kernel.org> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: Richard Henderson <rth@twiddle.net> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Christian Zankel <chris@zankel.net> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-06read_current_timer() cleanupsAndrew Morton
- All implementations can be __devinit - The function prototypes were in asm/timex.h but they all must be the same, so create a single declaration in linux/timex.h. - uninline the sparc64 version to match the other architectures - Don't bother #defining ARCH_HAS_READ_CURRENT_TIMER to a particular value. [ezk@cs.sunysb.edu: fix build] Cc: "David S. Miller" <davem@davemloft.net> Cc: Haavard Skinnemoen <hskinnemoen@atmel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-16slow down printk during bootRandy Dunlap
Optionally add a boot delay after each kernel printk() call, crudely measured in milliseconds, with a maximum delay of 10 seconds per printk. Enable CONFIG_BOOT_PRINTK_DELAY=y and then add (e.g.): "lpj=loops_per_jiffy boot_delay=100" to the kernel command line. It has been useful in cases like "during boot, my machine just reboots or the screen goes black" by slowing down printk, (and adding initcall_debug), we can usually see the last thing that happened before the lights went out which is usually a valuable clue. [akpm@linux-foundation.org: not all architectures implement CONFIG_HZ] [akpm@linux-foundation.org: fix lots of stuff] [bunk@stusta.de: kernel/printk.c: make 2 variables static] [heiko.carstens@de.ibm.com: fix slow down printk on boot compile error] Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Dave Jones <davej@redhat.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-14[PATCH] remove many unneeded #includes of sched.hTim Schmielau
After Al Viro (finally) succeeded in removing the sched.h #include in module.h recently, it makes sense again to remove other superfluous sched.h includes. There are quite a lot of files which include it but don't actually need anything defined in there. Presumably these includes were once needed for macros that used to live in sched.h, but moved to other header files in the course of cleaning it up. To ease the pain, this time I did not fiddle with any header files and only removed #includes from .c-files, which tend to cause less trouble. Compile tested against 2.6.20-rc2 and 2.6.20-rc2-mm2 (with offsets) on alpha, arm, i386, ia64, mips, powerpc, and x86_64 with allnoconfig, defconfig, allmodconfig, and allyesconfig as well as a few randconfigs on x86_64 and all configs in arch/arm/configs on arm. I also checked that no new warnings were introduced by the patch (actually, some warnings are removed that were emitted by unnecessarily included header files). Signed-off-by: Tim Schmielau <tim@physik3.uni-rostock.de> Acked-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2005-06-23[PATCH] Platform SMIs and their interferance with tsc based delay calibrationVenkatesh Pallipadi
Issue: Current tsc based delay_calibration can result in significant errors in loops_per_jiffy count when the platform events like SMIs (System Management Interrupts that are non-maskable) are present. This could lead to potential kernel panic(). This issue is becoming more visible with 2.6 kernel (as default HZ is 1000) and on platforms with higher SMI handling latencies. During the boot time, SMIs are mostly used by BIOS (for things like legacy keyboard emulation). Description: The psuedocode for current delay calibration with tsc based delay looks like (0) Estimate a value for loops_per_jiffy (1) While (loops_per_jiffy estimate is accurate enough) (2) wait for jiffy transition (jiffy1) (3) Note down current tsc (tsc1) (4) loop until tsc becomes tsc1 + loops_per_jiffy (5) check whether jiffy changed since jiffy1 or not and refine loops_per_jiffy estimate Consider the following cases Case 1: If SMIs happen between (2) and (3) above, we can end up with a loops_per_jiffy value that is too low. This results in shorted delays and kernel can panic () during boot (Mostly at IOAPIC timer initialization timer_irq_works() as we don't have enough timer interrupts in a specified interval). Case 2: If SMIs happen between (3) and (4) above, then we can end up with a loops_per_jiffy value that is too high. And with current i386 code, too high lpj value (greater than 17M) can result in a overflow in delay.c:__const_udelay() again resulting in shorter delay and panic(). Solution: The patch below makes the calibration routine aware of asynchronous events like SMIs. We increase the delay calibration time and also identify any significant errors (greater than 12.5%) in the calibration and notify it to user. Patch below changes both i386 and x86-64 architectures to use this new and improved calibrate_delay_direct() routine. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-04-16Linux-2.6.12-rc2v2.6.12-rc2Linus Torvalds
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!