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* nohz_full: Document additional restrictionsPaul E. McKenney2013-06-101-3/+18
| | | | | | | | | | | | This commit calls out the potential for slowing the tick even when there are multiple runnable processes per CPU, It also points out that current mainlined version keeps the tick going on at least one CPU even when all CPUs are otherwise idle. Finally, it notes the need for a 1-HZ tick in order to calculate CPU load, maintain sched average, compute CFS entity vruntime, compute avenrun, and carry out load balancing. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
* nohz_full: Update based on Sedat Dilek reviewPaul E. McKenney2013-06-101-9/+49
| | | | | | | | | | Make it more clear that there are three options, and give hints as to which of the three is most likely to be useful in different situations. Reported-by: Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
* nohz_full: Add documentation.Paul E. McKenney2013-04-271-0/+273
| | | | | | | | | | | | | | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Kevin Hilman <khilman@linaro.org> Cc: Christoph Lameter <cl@linux.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Olivier Baetz <olivier.baetz@novasparks.com> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Borislav Petkov <bp@suse.de> Reviewed-by: Kevin Hilman <khilman@linaro.org>
* doc: fix broken referencesPaul Bolle2011-09-271-1/+1
| | | | | | | | | | | | | There are numerous broken references to Documentation files (in other Documentation files, in comments, etc.). These broken references are caused by typo's in the references, and by renames or removals of the Documentation files. Some broken references are simply odd. Fix these broken references, sometimes by dropping the irrelevant text they were part of. Signed-off-by: Paul Bolle <pebolle@tiscali.nl> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
* doc: timers-howto: fix a typo ("unsgined")Jonathan Neuschäfer2011-05-171-1/+1
| | | | | Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
* tree-wide: fix comment/printk typosUwe Kleine-König2010-11-011-1/+1
| | | | | | | | | | "gadget", "through", "command", "maintain", "maintain", "controller", "address", "between", "initiali[zs]e", "instead", "function", "select", "already", "equal", "access", "management", "hierarchy", "registration", "interest", "relative", "memory", "offset", "already", Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
* Documentation/timers/hpet_example.c: add supporting info for hpet_exampleJaswinder Singh Rajput2010-10-261-0/+27
| | | | | | | | | | | | | | $./hpet_example info /dev/hpet -hpet: executing info hpet_info: hi_irqfreq 0x0 hi_flags 0x0 hi_hpet 0 hi_timer 2 Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com> Cc: Clemens Ladisch <clemens@ladisch.de> Cc: "Venkatesh Pallipadi (Venki)" <venki@google.com> Cc: john stultz <johnstul@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Documentation: Add timers/timers-howto.txtPatrick Pannuto2010-08-041-0/+105
| | | | | | | | | | | | | | | | | | | | | | | | | This file seeks to explain the nuances in various delays; many driver writers are not necessarily familiar with the various kernel timers, their shortfalls, and quirks. When faced with ndelay, udelay, mdelay, usleep_range, msleep, and msleep_interrubtible the question "How do I just wait 1 ms for my hardware to latch?" has the non-intuitive "best" answer: usleep_range(1000,1500) This patch is followed by a series of checkpatch additions that seek to help kernel hackers pick the best delay. Signed-off-by: Patrick Pannuto <ppannuto@codeaurora.org> Cc: apw@canonical.com Cc: corbet@lwn.net Cc: arjan@linux.intel.com Cc: Randy Dunlap <rdunlap@xenotime.net> Cc: Andrew Morton <akpm@linux-foundation.org> LKML-Reference: <1280786467-26999-3-git-send-email-ppannuto@codeaurora.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* Documentation/timers/hpet_example.c: only build on X86Randy Dunlap2010-06-011-1/+1
| | | | | | | | | | | We should only build hpet_example on x86[-64], where it is implemented. It can cause build errors on other architectures. Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Documentation/timers/hpet_example: drop duplicate header filesAndrea Gelmini2010-05-241-2/+0
| | | | | | | | | Documentation/timers/hpet_example.c: fcntl.h is included more than once. Documentation/timers/hpet_example.c: signal.h is included more than once. Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Documentation/timers/: split txt and source filesRandy Dunlap2010-03-124-271/+281
| | | | | | | | | | | | | | | | | | | | Documentation/timers/hpet.txt: Expose example and tool source files in the Documentation/timers/ directory in their own files instead of being buried (almost hidden) in readme/txt files. This should help to prevent bitrot. This will make them more visible/usable to users who may need to use them, to developers who may need to test with them, and to anyone who would fix/update them if they were more visible. Also, if any of these possibly should not be in the kernel tree at all, it will be clearer that they are here and we can discuss if they should be removed. Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fix URL in hpet.txtAmerigo Wang2009-11-091-1/+1
| | | | | | | | | | | | That URL is out of date. Update it. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Randy Dunlap <rdunlap@xenotime.net> Cc: Matt LaPlante <kernel1@cyberdogtech.com> Cc: Jiri Kosina <jkosina@suse.cz> Signed-off-by: WANG Cong <amwang@redhat.com> Acked-by: Matt LaPlante <kernel@cyberdogtech.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
* trivial: Miscellaneous documentation typo fixesMatt LaPlante2009-06-122-2/+2
| | | | | | | Fix various typos in documentation txts. Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
* hpet: /dev/hpet - fixes and cleanupDavid Brownell2008-07-311-22/+21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Minor /dev/hpet updates and bugfixes: * Remove dead code, mostly remnants of an incomplete/unusable kernel interface ... noted when addressing "sparse" warnings: + hpet_unregister() and a routine it calls + hpet_task and all references, including hpet_task_lock + hpet_data.hd_flags (and HPET_DATA_PLATFORM) * Correct and improve boot message: + displays *counter* (shared between comparators) bit width, not *timer* bit widths (which are often mixed) + relabel "timers" as "comparators"; this is less confusing, they are not independent like normal timers are (sigh) + display MHz not Hz; it's never less than 10 MHz. * Tighten and correct the userspace interface code + don't accidentally program comparators in 64-bit mode using 32-bit values ... always force comparators into 32-bit mode + provide the correct bit definition flagging comparators with periodic capability ... the ABI is unchanged * Update Documentation/hpet.txt + be more correct and current + expand description a bit + don't mention that now-gone kernel interface Plus, add a FIXME comment for something that could cause big trouble on systems with more capable HPETs than at least Intel seems to ship. It seems that few folk use this userspace interface; it's not very usable given the general lack of HPET IRQ routing. I'm told that the only real point of it any more is to mmap for fast timestamps; IMO that's handled better through the gettimeofday() vsyscall. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Acked-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Merge branch 'linus' into timers/hpetIngo Molnar2008-07-311-1/+1
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| * Documentation cleanup: trivial misspelling, punctuation, and grammar ↵Matt LaPlante2008-07-261-1/+1
| | | | | | | | | | | | | | | | corrections. Cc: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | documentation: move hpet.txt to timers/ subdirectoryRandy Dunlap2008-07-242-0/+310
|/ | | | | | | | | Move hpet.txt to Documentation/timers/ subdirectory. Add 00-INDEX to Documentation/timers/ subdirectory. Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Cc: tglx <tglx@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* Documentation: move timer related documentation to a single placeThomas Gleixner2008-04-173-0/+500
We have two directories with timer related information in Documentation/: hrtimers/ and hrtimer/. timer_stats are not restricted to hrtimers. Move all those files into Documentation/timers where we can pile up other timer related docs as well. Pointed-out-by: Randy Dunlap <randy@oracle.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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