03 Jul, 2013

1 commit

  • The posix cpu timer expiry time is stored in a union of two types: a 64
    bits field if we rely on scheduler precise accounting, or a cputime_t if
    we rely on jiffies.

    This results in quite some duplicate code and special cases to handle the
    two types.

    Just unify this into a single 64 bits field. cputime_t can always fit
    into it.

    Signed-off-by: Frederic Weisbecker
    Cc: Stanislaw Gruszka
    Cc: Thomas Gleixner
    Cc: Peter Zijlstra
    Cc: Ingo Molnar
    Cc: Oleg Nesterov
    Cc: KOSAKI Motohiro
    Cc: Olivier Langlois
    Signed-off-by: Andrew Morton

    Frederic Weisbecker
     

06 May, 2013

1 commit

  • Pull 'full dynticks' support from Ingo Molnar:
    "This tree from Frederic Weisbecker adds a new, (exciting! :-) core
    kernel feature to the timer and scheduler subsystems: 'full dynticks',
    or CONFIG_NO_HZ_FULL=y.

    This feature extends the nohz variable-size timer tick feature from
    idle to busy CPUs (running at most one task) as well, potentially
    reducing the number of timer interrupts significantly.

    This feature got motivated by real-time folks and the -rt tree, but
    the general utility and motivation of full-dynticks runs wider than
    that:

    - HPC workloads get faster: CPUs running a single task should be able
    to utilize a maximum amount of CPU power. A periodic timer tick at
    HZ=1000 can cause a constant overhead of up to 1.0%. This feature
    removes that overhead - and speeds up the system by 0.5%-1.0% on
    typical distro configs even on modern systems.

    - Real-time workload latency reduction: CPUs running critical tasks
    should experience as little jitter as possible. The last remaining
    source of kernel-related jitter was the periodic timer tick.

    - A single task executing on a CPU is a pretty common situation,
    especially with an increasing number of cores/CPUs, so this feature
    helps desktop and mobile workloads as well.

    The cost of the feature is mainly related to increased timer
    reprogramming overhead when a CPU switches its tick period, and thus
    slightly longer to-idle and from-idle latency.

    Configuration-wise a third mode of operation is added to the existing
    two NOHZ kconfig modes:

    - CONFIG_HZ_PERIODIC: [formerly !CONFIG_NO_HZ], now explicitly named
    as a config option. This is the traditional Linux periodic tick
    design: there's a HZ tick going on all the time, regardless of
    whether a CPU is idle or not.

    - CONFIG_NO_HZ_IDLE: [formerly CONFIG_NO_HZ=y], this turns off the
    periodic tick when a CPU enters idle mode.

    - CONFIG_NO_HZ_FULL: this new mode, in addition to turning off the
    tick when a CPU is idle, also slows the tick down to 1 Hz (one
    timer interrupt per second) when only a single task is running on a
    CPU.

    The .config behavior is compatible: existing !CONFIG_NO_HZ and
    CONFIG_NO_HZ=y settings get translated to the new values, without the
    user having to configure anything. CONFIG_NO_HZ_FULL is turned off by
    default.

    This feature is based on a lot of infrastructure work that has been
    steadily going upstream in the last 2-3 cycles: related RCU support
    and non-periodic cputime support in particular is upstream already.

    This tree adds the final pieces and activates the feature. The pull
    request is marked RFC because:

    - it's marked 64-bit only at the moment - the 32-bit support patch is
    small but did not get ready in time.

    - it has a number of fresh commits that came in after the merge
    window. The overwhelming majority of commits are from before the
    merge window, but still some aspects of the tree are fresh and so I
    marked it RFC.

    - it's a pretty wide-reaching feature with lots of effects - and
    while the components have been in testing for some time, the full
    combination is still not very widely used. That it's default-off
    should reduce its regression abilities and obviously there are no
    known regressions with CONFIG_NO_HZ_FULL=y enabled either.

    - the feature is not completely idempotent: there is no 100%
    equivalent replacement for a periodic scheduler/timer tick. In
    particular there's ongoing work to map out and reduce its effects
    on scheduler load-balancing and statistics. This should not impact
    correctness though, there are no known regressions related to this
    feature at this point.

    - it's a pretty ambitious feature that with time will likely be
    enabled by most Linux distros, and we'd like you to make input on
    its design/implementation, if you dislike some aspect we missed.
    Without flaming us to crisp! :-)

    Future plans:

    - there's ongoing work to reduce 1Hz to 0Hz, to essentially shut off
    the periodic tick altogether when there's a single busy task on a
    CPU. We'd first like 1 Hz to be exposed more widely before we go
    for the 0 Hz target though.

    - once we reach 0 Hz we can remove the periodic tick assumption from
    nr_running>=2 as well, by essentially interrupting busy tasks only
    as frequently as the sched_latency constraints require us to do -
    once every 4-40 msecs, depending on nr_running.

    I am personally leaning towards biting the bullet and doing this in
    v3.10, like the -rt tree this effort has been going on for too long -
    but the final word is up to you as usual.

    More technical details can be found in Documentation/timers/NO_HZ.txt"

    * 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits)
    sched: Keep at least 1 tick per second for active dynticks tasks
    rcu: Fix full dynticks' dependency on wide RCU nocb mode
    nohz: Protect smp_processor_id() in tick_nohz_task_switch()
    nohz_full: Add documentation.
    cputime_nsecs: use math64.h for nsec resolution conversion helpers
    nohz: Select VIRT_CPU_ACCOUNTING_GEN from full dynticks config
    nohz: Reduce overhead under high-freq idling patterns
    nohz: Remove full dynticks' superfluous dependency on RCU tree
    nohz: Fix unavailable tick_stop tracepoint in dynticks idle
    nohz: Add basic tracing
    nohz: Select wide RCU nocb for full dynticks
    nohz: Disable the tick when irq resume in full dynticks CPU
    nohz: Re-evaluate the tick for the new task after a context switch
    nohz: Prepare to stop the tick on irq exit
    nohz: Implement full dynticks kick
    nohz: Re-evaluate the tick from the scheduler IPI
    sched: New helper to prevent from stopping the tick in full dynticks
    sched: Kick full dynticks CPU that have more than one task enqueued.
    perf: New helper to prevent full dynticks CPUs from stopping tick
    perf: Kick full dynticks CPU if events rotation is needed
    ...

    Linus Torvalds
     

19 Apr, 2013

1 commit

  • Bring a new helper that the full dynticks infrastructure can
    call in order to know if it can safely stop the tick from
    the posix cpu timers subsystem point of view.

    Signed-off-by: Frederic Weisbecker
    Cc: Chris Metcalf
    Cc: Christoph Lameter
    Cc: Geoff Levand
    Cc: Gilad Ben Yossef
    Cc: Hakan Akkan
    Cc: Ingo Molnar
    Cc: Kevin Hilman
    Cc: Li Zhong
    Cc: Oleg Nesterov
    Cc: Paul E. McKenney
    Cc: Paul Gortmaker
    Cc: Peter Zijlstra
    Cc: Steven Rostedt
    Cc: Thomas Gleixner

    Frederic Weisbecker
     

18 Apr, 2013

1 commit

  • Currently kernel generates IDs for posix timers in a global manner --
    there's a kernel-wide IDR tree from which IDs are created. This makes
    it impossible to recreate a timer with a desired ID (in particular
    this is done by the CRIU checkpoint-restore project) -- since these
    IDs are global it may happen, that at the time we recreate a timer, the
    ID we want for it is already busy by some other timer.

    In order to address this, replace the IDR tree with a global hash
    table for timers and makes timer IDs unique per signal_struct (to
    which timers are linked anyway). With this, two timers belonging to
    different processes may have equal IDs and we can recreate either of
    them with the ID we want.

    Signed-off-by: Pavel Emelyanov
    Cc: Peter Zijlstra
    Cc: Michael Kerrisk
    Cc: Matthew Helsley
    Link: http://lkml.kernel.org/r/513D9FF5.9010004@parallels.com
    Signed-off-by: Thomas Gleixner

    Pavel Emelyanov
     

11 Aug, 2011

1 commit


24 May, 2011

1 commit

  • Ben Nagy reported a scalability problem with KVM/QEMU that hit very hard
    a single spinlock (idr_lock) in posix-timers code, on its 48 core
    machine.

    Even on a 16 cpu machine (2x4x2), a single test can show 98% of cpu time
    used in ticket_spin_lock, from lock_timer

    Ref: http://www.spinics.net/lists/kvm/msg51526.html

    Switching to RCU is quite easy, IDR being already RCU ready. idr_lock
    should be locked only for an insert/delete, not a lookup.

    Benchmark on a 2x4x2 machine, 16 processes calling timer_gettime().

    Before :

    real 1m18.669s
    user 0m1.346s
    sys 1m17.180s

    After :

    real 0m3.296s
    user 0m1.366s
    sys 0m1.926s

    Reported-by: Ben Nagy
    Signed-off-by: Eric Dumazet
    Tested-by: Ben Nagy
    Cc: Oleg Nesterov
    Cc: Avi Kivity
    Cc: John Stultz
    Cc: Richard Cochran
    Cc: Paul E. McKenney
    Cc: Andrew Morton
    Signed-off-by: Thomas Gleixner

    Eric Dumazet
     

27 Apr, 2011

1 commit

  • This patch exposes alarm-timers to userland via the posix clock
    and timers interface, using two new clockids: CLOCK_REALTIME_ALARM
    and CLOCK_BOOTTIME_ALARM. Both clockids behave identically to
    CLOCK_REALTIME and CLOCK_BOOTTIME, respectively, but timers
    set against the _ALARM suffixed clockids will wake the system if
    it is suspended.

    Some background can be found here:
    https://lwn.net/Articles/429925/

    The concept for Alarm-timers was inspired by the Android Alarm
    driver (by Arve Hjønnevåg) found in the Android kernel tree.

    See: http://android.git.kernel.org/?p=kernel/common.git;a=blob;f=drivers/rtc/alarm.c;h=1250edfbdf3302f5e4ea6194847c6ef4bb7beb1c;hb=android-2.6.36

    While the in-kernel interface is pretty similar between
    alarm-timers and Android alarm driver, the user-space interface
    for the Android alarm driver is via ioctls to a new char device.
    As mentioned above, I've instead chosen to export this functionality
    via the posix interface, as it seemed a little simpler and avoids
    creating duplicate interfaces to things like CLOCK_REALTIME and
    CLOCK_MONOTONIC under alternate names (ie:ANDROID_ALARM_RTC and
    ANDROID_ALARM_SYSTEMTIME).

    The semantics of the Android alarm driver are different from what
    this posix interface provides. For instance, threads other then
    the thread waiting on the Android alarm driver are able to modify
    the alarm being waited on. Also this interface does not allow
    the same wakelock semantics that the Android driver provides
    (ie: kernel takes a wakelock on RTC alarm-interupt, and holds it
    through process wakeup, and while the process runs, until the
    process either closes the char device or calls back in to wait
    on a new alarm).

    One potential way to implement similar semantics may be via
    the timerfd infrastructure, but this needs more research.

    There may also need to be some sort of sysfs system level policy
    hooks that allow alarm timers to be disabled to keep them
    from firing at inappropriate times (ie: laptop in a well insulated
    bag, mid-flight).

    CC: Arve Hjønnevåg
    CC: Thomas Gleixner
    CC: Alessandro Zummo
    Acked-by: Arnd Bergmann
    Signed-off-by: John Stultz

    John Stultz
     

02 Feb, 2011

10 commits

  • This patch adds support for adding and removing posix clocks. The
    clock lifetime cycle is patterned after usb devices. Each clock is
    represented by a standard character device. In addition, the driver
    may optionally implement custom character device operations.

    The posix clock and timer system calls listed below now work with
    dynamic posix clocks, as well as the traditional static clocks.
    The following system calls are affected:

    - clock_adjtime (brand new syscall)
    - clock_gettime
    - clock_getres
    - clock_settime
    - timer_create
    - timer_delete
    - timer_gettime
    - timer_settime

    [ tglx: Adapted to the posix-timer cleanup. Moved clock_posix_dynamic
    to posix-clock.c and made all referenced functions static ]

    Signed-off-by: Richard Cochran
    Acked-by: John Stultz
    LKML-Reference:
    Signed-off-by: Thomas Gleixner

    Richard Cochran
     
  • Rename register_posix_clock() to posix_timers_register_clock(). That's
    what the function really does. As a side effect this cleans up the
    posix_clock namespace for the upcoming dynamic posix_clock
    infrastructure.

    Signed-off-by: Thomas Gleixner
    Tested-by: Richard Cochran
    Cc: John Stultz
    LKML-Reference:

    Thomas Gleixner
     
  • Extend the negative clockids which are currently used by posix cpu
    timers to encode the PID with a file descriptor based type which
    encodes the fd in the upper bits.

    Originally-from: Richard Cochran
    Signed-off-by: Thomas Gleixner
    Acked-by: John Stultz
    LKML-Reference:

    Richard Cochran
     
  • A new syscall is introduced that allows tuning of a POSIX clock. The
    new call, clock_adjtime, takes two parameters, the clock ID and a
    pointer to a struct timex. Any ADJTIMEX(2) operation may be requested
    via this system call, but various POSIX clocks may or may not support
    tuning.

    [ tglx: Adapted to the posix-timer cleanup series. Avoid copy_to_user
    in the error case ]

    Signed-off-by: Richard Cochran
    Acked-by: John Stultz
    LKML-Reference:
    Signed-off-by: Thomas Gleixner

    Richard Cochran
     
  • All functions are accessed via clock_posix_cpu now. So make them static.

    Signed-off-by: Thomas Gleixner
    Acked-by: John Stultz
    Tested-by: Richard Cochran
    LKML-Reference:

    Thomas Gleixner
     
  • The res member of kclock is only used by mmtimer.c, but even there it
    contains redundant information. Remove the field and fixup mmtimer.

    Signed-off-by: Thomas Gleixner
    Acked-by: John Stultz
    Tested-by: Richard Cochran
    LKML-Reference:

    Thomas Gleixner
     
  • Use the new kclock decoding function in clock_settime and cleanup all
    kclocks which use the default functions. Rename the misnomed
    common_clock_set() to posix_clock_realtime_set().

    Signed-off-by: Thomas Gleixner
    Acked-by: John Stultz
    Tested-by: Richard Cochran
    LKML-Reference:

    Thomas Gleixner
     
  • Use the new kclock decoding function in clock_nanosleep and cleanup all
    kclocks which use the default functions.

    Signed-off-by: Thomas Gleixner
    Acked-by: John Stultz
    Tested-by: Richard Cochran
    LKML-Reference:

    Thomas Gleixner
     
  • The CLOCK_DISPATCH() macro is a horrible magic. We call common
    functions if a function pointer is not set. That's just backwards.

    To support dynamic file decriptor based clocks we need to cleanup that
    dispatch logic.

    Create a k_clock struct clock_posix_cpu which has all the
    posix-cpu-timer functions filled in. After the cleanup the functions
    can be made static.

    Signed-off-by: Thomas Gleixner
    Acked-by: John Stultz
    Tested-by: Richard Cochran
    LKML-Reference:

    Thomas Gleixner
     
  • Both settimeofday() and clock_settime() promise with a 'const'
    attribute not to alter the arguments passed in. This patch adds the
    missing 'const' attribute into the various kernel functions
    implementing these calls.

    Signed-off-by: Richard Cochran
    Acked-by: John Stultz
    LKML-Reference:
    Signed-off-by: Thomas Gleixner

    Richard Cochran
     

16 Jul, 2010

1 commit


13 Dec, 2008

1 commit

  • Impact: restructure, clean up code

    k_itimer holds the ref to the ->it_process until sys_timer_delete(). This
    allows to pin up to RLIMIT_SIGPENDING dead task_struct's. Change the code
    to use "struct pid *" instead.

    The patch doesn't kill ->it_process, it places ->it_pid into the union.
    ->it_process is still used by do_cpu_nanosleep() as before. It would be
    trivial to change the nanosleep code as well, but since it uses it_process
    in a special way I think it is better to keep this field for grep.

    The patch bloats the kernel by 104 bytes and it also adds the new pointer,
    ->it_signal, to k_itimer. It is used by lock_timer() to verify that the
    found timer was not created by another process. It is not clear why do we
    use the global database (and thus the global idr_lock) for posix timers.
    We still need the signal_struct->posix_timers which contains all useable
    timers, perhaps it is better to use some form of per-process array
    instead.

    Signed-off-by: Oleg Nesterov
    Signed-off-by: Andrew Morton
    Signed-off-by: Thomas Gleixner

    Oleg Nesterov
     

24 Sep, 2008

1 commit


14 Sep, 2008

1 commit

  • Overview

    This patch reworks the handling of POSIX CPU timers, including the
    ITIMER_PROF, ITIMER_VIRT timers and rlimit handling. It was put together
    with the help of Roland McGrath, the owner and original writer of this code.

    The problem we ran into, and the reason for this rework, has to do with using
    a profiling timer in a process with a large number of threads. It appears
    that the performance of the old implementation of run_posix_cpu_timers() was
    at least O(n*3) (where "n" is the number of threads in a process) or worse.
    Everything is fine with an increasing number of threads until the time taken
    for that routine to run becomes the same as or greater than the tick time, at
    which point things degrade rather quickly.

    This patch fixes bug 9906, "Weird hang with NPTL and SIGPROF."

    Code Changes

    This rework corrects the implementation of run_posix_cpu_timers() to make it
    run in constant time for a particular machine. (Performance may vary between
    one machine and another depending upon whether the kernel is built as single-
    or multiprocessor and, in the latter case, depending upon the number of
    running processors.) To do this, at each tick we now update fields in
    signal_struct as well as task_struct. The run_posix_cpu_timers() function
    uses those fields to make its decisions.

    We define a new structure, "task_cputime," to contain user, system and
    scheduler times and use these in appropriate places:

    struct task_cputime {
    cputime_t utime;
    cputime_t stime;
    unsigned long long sum_exec_runtime;
    };

    This is included in the structure "thread_group_cputime," which is a new
    substructure of signal_struct and which varies for uniprocessor versus
    multiprocessor kernels. For uniprocessor kernels, it uses "task_cputime" as
    a simple substructure, while for multiprocessor kernels it is a pointer:

    struct thread_group_cputime {
    struct task_cputime totals;
    };

    struct thread_group_cputime {
    struct task_cputime *totals;
    };

    We also add a new task_cputime substructure directly to signal_struct, to
    cache the earliest expiration of process-wide timers, and task_cputime also
    replaces the it_*_expires fields of task_struct (used for earliest expiration
    of thread timers). The "thread_group_cputime" structure contains process-wide
    timers that are updated via account_user_time() and friends. In the non-SMP
    case the structure is a simple aggregator; unfortunately in the SMP case that
    simplicity was not achievable due to cache-line contention between CPUs (in
    one measured case performance was actually _worse_ on a 16-cpu system than
    the same test on a 4-cpu system, due to this contention). For SMP, the
    thread_group_cputime counters are maintained as a per-cpu structure allocated
    using alloc_percpu(). The timer functions update only the timer field in
    the structure corresponding to the running CPU, obtained using per_cpu_ptr().

    We define a set of inline functions in sched.h that we use to maintain the
    thread_group_cputime structure and hide the differences between UP and SMP
    implementations from the rest of the kernel. The thread_group_cputime_init()
    function initializes the thread_group_cputime structure for the given task.
    The thread_group_cputime_alloc() is a no-op for UP; for SMP it calls the
    out-of-line function thread_group_cputime_alloc_smp() to allocate and fill
    in the per-cpu structures and fields. The thread_group_cputime_free()
    function, also a no-op for UP, in SMP frees the per-cpu structures. The
    thread_group_cputime_clone_thread() function (also a UP no-op) for SMP calls
    thread_group_cputime_alloc() if the per-cpu structures haven't yet been
    allocated. The thread_group_cputime() function fills the task_cputime
    structure it is passed with the contents of the thread_group_cputime fields;
    in UP it's that simple but in SMP it must also safely check that tsk->signal
    is non-NULL (if it is it just uses the appropriate fields of task_struct) and,
    if so, sums the per-cpu values for each online CPU. Finally, the three
    functions account_group_user_time(), account_group_system_time() and
    account_group_exec_runtime() are used by timer functions to update the
    respective fields of the thread_group_cputime structure.

    Non-SMP operation is trivial and will not be mentioned further.

    The per-cpu structure is always allocated when a task creates its first new
    thread, via a call to thread_group_cputime_clone_thread() from copy_signal().
    It is freed at process exit via a call to thread_group_cputime_free() from
    cleanup_signal().

    All functions that formerly summed utime/stime/sum_sched_runtime values from
    from all threads in the thread group now use thread_group_cputime() to
    snapshot the values in the thread_group_cputime structure or the values in
    the task structure itself if the per-cpu structure hasn't been allocated.

    Finally, the code in kernel/posix-cpu-timers.c has changed quite a bit.
    The run_posix_cpu_timers() function has been split into a fast path and a
    slow path; the former safely checks whether there are any expired thread
    timers and, if not, just returns, while the slow path does the heavy lifting.
    With the dedicated thread group fields, timers are no longer "rebalanced" and
    the process_timer_rebalance() function and related code has gone away. All
    summing loops are gone and all code that used them now uses the
    thread_group_cputime() inline. When process-wide timers are set, the new
    task_cputime structure in signal_struct is used to cache the earliest
    expiration; this is checked in the fast path.

    Performance

    The fix appears not to add significant overhead to existing operations. It
    generally performs the same as the current code except in two cases, one in
    which it performs slightly worse (Case 5 below) and one in which it performs
    very significantly better (Case 2 below). Overall it's a wash except in those
    two cases.

    I've since done somewhat more involved testing on a dual-core Opteron system.

    Case 1: With no itimer running, for a test with 100,000 threads, the fixed
    kernel took 1428.5 seconds, 513 seconds more than the unfixed system,
    all of which was spent in the system. There were twice as many
    voluntary context switches with the fix as without it.

    Case 2: With an itimer running at .01 second ticks and 4000 threads (the most
    an unmodified kernel can handle), the fixed kernel ran the test in
    eight percent of the time (5.8 seconds as opposed to 70 seconds) and
    had better tick accuracy (.012 seconds per tick as opposed to .023
    seconds per tick).

    Case 3: A 4000-thread test with an initial timer tick of .01 second and an
    interval of 10,000 seconds (i.e. a timer that ticks only once) had
    very nearly the same performance in both cases: 6.3 seconds elapsed
    for the fixed kernel versus 5.5 seconds for the unfixed kernel.

    With fewer threads (eight in these tests), the Case 1 test ran in essentially
    the same time on both the modified and unmodified kernels (5.2 seconds versus
    5.8 seconds). The Case 2 test ran in about the same time as well, 5.9 seconds
    versus 5.4 seconds but again with much better tick accuracy, .013 seconds per
    tick versus .025 seconds per tick for the unmodified kernel.

    Since the fix affected the rlimit code, I also tested soft and hard CPU limits.

    Case 4: With a hard CPU limit of 20 seconds and eight threads (and an itimer
    running), the modified kernel was very slightly favored in that while
    it killed the process in 19.997 seconds of CPU time (5.002 seconds of
    wall time), only .003 seconds of that was system time, the rest was
    user time. The unmodified kernel killed the process in 20.001 seconds
    of CPU (5.014 seconds of wall time) of which .016 seconds was system
    time. Really, though, the results were too close to call. The results
    were essentially the same with no itimer running.

    Case 5: With a soft limit of 20 seconds and a hard limit of 2000 seconds
    (where the hard limit would never be reached) and an itimer running,
    the modified kernel exhibited worse tick accuracy than the unmodified
    kernel: .050 seconds/tick versus .028 seconds/tick. Otherwise,
    performance was almost indistinguishable. With no itimer running this
    test exhibited virtually identical behavior and times in both cases.

    In times past I did some limited performance testing. those results are below.

    On a four-cpu Opteron system without this fix, a sixteen-thread test executed
    in 3569.991 seconds, of which user was 3568.435s and system was 1.556s. On
    the same system with the fix, user and elapsed time were about the same, but
    system time dropped to 0.007 seconds. Performance with eight, four and one
    thread were comparable. Interestingly, the timer ticks with the fix seemed
    more accurate: The sixteen-thread test with the fix received 149543 ticks
    for 0.024 seconds per tick, while the same test without the fix received 58720
    for 0.061 seconds per tick. Both cases were configured for an interval of
    0.01 seconds. Again, the other tests were comparable. Each thread in this
    test computed the primes up to 25,000,000.

    I also did a test with a large number of threads, 100,000 threads, which is
    impossible without the fix. In this case each thread computed the primes only
    up to 10,000 (to make the runtime manageable). System time dominated, at
    1546.968 seconds out of a total 2176.906 seconds (giving a user time of
    629.938s). It received 147651 ticks for 0.015 seconds per tick, still quite
    accurate. There is obviously no comparable test without the fix.

    Signed-off-by: Frank Mayhar
    Cc: Roland McGrath
    Cc: Alexey Dobriyan
    Cc: Andrew Morton
    Signed-off-by: Ingo Molnar

    Frank Mayhar
     

30 Sep, 2006

1 commit

  • The clock_nanosleep() function does not return the time remaining when the
    sleep is interrupted by a signal.

    This patch creates a new call out, compat_clock_nanosleep_restart(), which
    handles returning the remaining time after a sleep is interrupted. This
    patch revives clock_nanosleep_restart(). It is now accessed via the new
    call out. The compat_clock_nanosleep_restart() is used for compatibility
    access.

    Since this is implemented in compatibility mode the normal path is
    virtually unaffected - no real performance impact.

    Signed-off-by: Toyo Abe
    Cc: Thomas Gleixner
    Cc: Ingo Molnar
    Cc: Roland McGrath
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Toyo Abe
     

02 Feb, 2006

1 commit


11 Jan, 2006

4 commits


17 Apr, 2005

1 commit

  • 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!

    Linus Torvalds