1. 03 2月, 2010 1 次提交
  2. 15 1月, 2010 1 次提交
    • S
      powerpc: Fix decrementer setup on 1GHz boards · 3e7b4843
      Stefan Roese 提交于
      We noticed that recent kernels didn't boot on our 1GHz Canyonlands 460EX
      boards anymore. As it seems, patch 8d165db1 [powerpc: Improve
      decrementer accuracy] introduced this problem. The routine div_sc()
      overflows with shift = 32 resulting in this incorrect setup:
      
      time_init: decrementer frequency = 1000.000012 MHz
      time_init: processor frequency   = 1000.000012 MHz
      clocksource: timebase mult[400000] shift[22] registered
      clockevent: decrementer mult[33] shift[32] cpu[0]
      
      This patch now introduces a local div_dc64() version of this function
      so that this overflow doesn't happen anymore.
      Signed-off-by: NStefan Roese <sr@denx.de>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Detlev Zundel <dzu@denx.de>
      Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
      3e7b4843
  3. 17 11月, 2009 1 次提交
    • L
      timekeeping: Fix clock_gettime vsyscall time warp · 0696b711
      Lin Ming 提交于
      Since commit 0a544198 "timekeeping: Move NTP adjusted clock multiplier
      to struct timekeeper" the clock multiplier of vsyscall is updated with
      the unmodified clock multiplier of the clock source and not with the
      NTP adjusted multiplier of the timekeeper.
      
      This causes user space observerable time warps:
      new CLOCK-warp maximum: 120 nsecs,  00000025c337c537 -> 00000025c337c4bf
      
      Add a new argument "mult" to update_vsyscall() and hand in the
      timekeeping internal NTP adjusted multiplier.
      Signed-off-by: NLin Ming <ming.m.lin@intel.com>
      Cc: "Zhang Yanmin" <yanmin_zhang@linux.intel.com>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Tony Luck <tony.luck@intel.com>
      LKML-Reference: <1258436990.17765.83.camel@minggr.sh.intel.com>
      Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      0696b711
  4. 14 11月, 2009 1 次提交
    • T
      clocksource/events: Fix fallout of generic code changes · a362c638
      Thomas Gleixner 提交于
      powerpc grew a new warning due to the type change of clockevent->mult.
      
      The architectures which use parts of the generic time keeping
      infrastructure tripped over my wrong assumption that
      clocksource_register is only used when GENERIC_TIME=y.
      
      I should have looked and also I should have known better. These
      renitent Gaul villages are racking my nerves. Some serious deprecating
      is due.
      Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      a362c638
  5. 05 11月, 2009 2 次提交
  6. 28 10月, 2009 1 次提交
    • A
      powerpc: tracing: Add powerpc tracepoints for timer entry and exit · 6795b85c
      Anton Blanchard 提交于
      We can monitor the effectiveness of our power management of both the
      kernel and hypervisor by probing the timer interrupt. For example, on
      this box we see 10.37s timer interrupts on an idle core:
      
      <idle>-0     [010]  3900.671297: timer_interrupt_entry: pt_regs=c0000000ce1e7b10
      <idle>-0     [010]  3900.671302: timer_interrupt_exit: pt_regs=c0000000ce1e7b10
      
      <idle>-0     [010]  3911.042963: timer_interrupt_entry: pt_regs=c0000000ce1e7b10
      <idle>-0     [010]  3911.042968: timer_interrupt_exit: pt_regs=c0000000ce1e7b10
      
      <idle>-0     [010]  3921.414630: timer_interrupt_entry: pt_regs=c0000000ce1e7b10
      <idle>-0     [010]  3921.414635: timer_interrupt_exit: pt_regs=c0000000ce1e7b10
      
      Since we have a 207MHz decrementer it will go negative and fire every 10.37s
      even if Linux is completely idle.
      Signed-off-by: NAnton Blanchard <anton@samba.org>
      Signed-off-by: NPaul Mackerras <paulus@samba.org>
      6795b85c
  7. 21 9月, 2009 1 次提交
    • I
      perf: Do the big rename: Performance Counters -> Performance Events · cdd6c482
      Ingo Molnar 提交于
      Bye-bye Performance Counters, welcome Performance Events!
      
      In the past few months the perfcounters subsystem has grown out its
      initial role of counting hardware events, and has become (and is
      becoming) a much broader generic event enumeration, reporting, logging,
      monitoring, analysis facility.
      
      Naming its core object 'perf_counter' and naming the subsystem
      'perfcounters' has become more and more of a misnomer. With pending
      code like hw-breakpoints support the 'counter' name is less and
      less appropriate.
      
      All in one, we've decided to rename the subsystem to 'performance
      events' and to propagate this rename through all fields, variables
      and API names. (in an ABI compatible fashion)
      
      The word 'event' is also a bit shorter than 'counter' - which makes
      it slightly more convenient to write/handle as well.
      
      Thanks goes to Stephane Eranian who first observed this misnomer and
      suggested a rename.
      
      User-space tooling and ABI compatibility is not affected - this patch
      should be function-invariant. (Also, defconfigs were not touched to
      keep the size down.)
      
      This patch has been generated via the following script:
      
        FILES=$(find * -type f | grep -vE 'oprofile|[^K]config')
      
        sed -i \
          -e 's/PERF_EVENT_/PERF_RECORD_/g' \
          -e 's/PERF_COUNTER/PERF_EVENT/g' \
          -e 's/perf_counter/perf_event/g' \
          -e 's/nb_counters/nb_events/g' \
          -e 's/swcounter/swevent/g' \
          -e 's/tpcounter_event/tp_event/g' \
          $FILES
      
        for N in $(find . -name perf_counter.[ch]); do
          M=$(echo $N | sed 's/perf_counter/perf_event/g')
          mv $N $M
        done
      
        FILES=$(find . -name perf_event.*)
      
        sed -i \
          -e 's/COUNTER_MASK/REG_MASK/g' \
          -e 's/COUNTER/EVENT/g' \
          -e 's/\<event\>/event_id/g' \
          -e 's/counter/event/g' \
          -e 's/Counter/Event/g' \
          $FILES
      
      ... to keep it as correct as possible. This script can also be
      used by anyone who has pending perfcounters patches - it converts
      a Linux kernel tree over to the new naming. We tried to time this
      change to the point in time where the amount of pending patches
      is the smallest: the end of the merge window.
      
      Namespace clashes were fixed up in a preparatory patch - and some
      stylistic fallout will be fixed up in a subsequent patch.
      
      ( NOTE: 'counters' are still the proper terminology when we deal
        with hardware registers - and these sed scripts are a bit
        over-eager in renaming them. I've undone some of that, but
        in case there's something left where 'counter' would be
        better than 'event' we can undo that on an individual basis
        instead of touching an otherwise nicely automated patch. )
      Suggested-by: NStephane Eranian <eranian@google.com>
      Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
      Acked-by: NPaul Mackerras <paulus@samba.org>
      Reviewed-by: NArjan van de Ven <arjan@linux.intel.com>
      Cc: Mike Galbraith <efault@gmx.de>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: David Howells <dhowells@redhat.com>
      Cc: Kyle McMartin <kyle@mcmartin.ca>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: <linux-arch@vger.kernel.org>
      LKML-Reference: <new-submission>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      cdd6c482
  8. 28 8月, 2009 1 次提交
  9. 23 8月, 2009 1 次提交
  10. 20 8月, 2009 1 次提交
  11. 15 8月, 2009 1 次提交
  12. 03 8月, 2009 1 次提交
  13. 18 6月, 2009 1 次提交
    • P
      perf_counter: powerpc: Enable use of software counters on 32-bit powerpc · 105988c0
      Paul Mackerras 提交于
      This enables the perf_counter subsystem on 32-bit powerpc.  Since we
      don't have any support for hardware counters on 32-bit powerpc yet,
      only software counters can be used.
      
      Besides selecting HAVE_PERF_COUNTERS for 32-bit powerpc as well as
      64-bit, the main thing this does is add an implementation of
      set_perf_counter_pending().  This needs to arrange for
      perf_counter_do_pending() to be called when interrupts are enabled.
      Rather than add code to local_irq_restore as 64-bit does, the 32-bit
      set_perf_counter_pending() generates an interrupt by setting the
      decrementer to 1 so that a decrementer interrupt will become pending
      in 1 or 2 timebase ticks (if a decrementer interrupt isn't already
      pending).  When interrupts are enabled, timer_interrupt() will be
      called, and some new code in there calls perf_counter_do_pending().
      We use a per-cpu array of flags to indicate whether we need to call
      perf_counter_do_pending() or not.
      
      This introduces a couple of new Kconfig symbols: PPC_HAVE_PMU_SUPPORT,
      which is selected by processor families for which we have hardware PMU
      support (currently only PPC64), and PPC_PERF_CTRS, which enables the
      powerpc-specific perf_counter back-end.
      Signed-off-by: NPaul Mackerras <paulus@samba.org>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: linuxppc-dev@ozlabs.org
      Cc: benh@kernel.crashing.org
      LKML-Reference: <19000.55404.103840.393470@cargo.ozlabs.ibm.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      105988c0
  14. 15 6月, 2009 1 次提交
  15. 21 5月, 2009 1 次提交
    • A
      powerpc: Improve decrementer accuracy · 8d165db1
      Anton Blanchard 提交于
      I have been looking at sources of OS jitter and notice that after a long
      NO_HZ idle period we wakeup too early:
      
      relative time (us)    event
                            timer irq exit
          999946.405        timer irq entry
               4.835        timer irq exit
              21.685        timer irq entry
               3.540          timer (tick_sched_timer) entry
      
      Here we slept for just under a second then took a timer interrupt that did
      nothing. 21.685 us later we wake up again and do the work.
      
      We set a rather low shift value of 16 for the decrementer clockevent, which I
      think is causing this issue. On this box we have a 207MHz decrementer and see:
      
      clockevent: decrementer mult[3501] shift[16] cpu[0]
      
      For calculations of large intervals this mult/shift combination could be
      off by a significant amount. I notice the sparc code has a loop that iterates
      to find a mult/shift combination that maximises the shift value while
      keeping mult under 32bit. With the patch below we get:
      
      clockevent: decrementer mult[35015c20] shift[32] cpu[15]
      
      And we no longer see the spurious wakeups.
      Signed-off-by: NAnton Blanchard <anton@samba.org>
      Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
      8d165db1
  16. 22 4月, 2009 1 次提交
  17. 02 4月, 2009 1 次提交
  18. 31 12月, 2008 2 次提交
    • M
      [PATCH] idle cputime accounting · 79741dd3
      Martin Schwidefsky 提交于
      The cpu time spent by the idle process actually doing something is
      currently accounted as idle time. This is plain wrong, the architectures
      that support VIRT_CPU_ACCOUNTING=y can do better: distinguish between the
      time spent doing nothing and the time spent by idle doing work. The first
      is accounted with account_idle_time and the second with account_system_time.
      The architectures that use the account_xxx_time interface directly and not
      the account_xxx_ticks interface now need to do the check for the idle
      process in their arch code. In particular to improve the system vs true
      idle time accounting the arch code needs to measure the true idle time
      instead of just testing for the idle process.
      To improve the tick based accounting as well we would need an architecture
      primitive that can tell us if the pt_regs of the interrupted context
      points to the magic instruction that halts the cpu.
      
      In addition idle time is no more added to the stime of the idle process.
      This field now contains the system time of the idle process as it should
      be. On systems without VIRT_CPU_ACCOUNTING this will always be zero as
      every tick that occurs while idle is running will be accounted as idle
      time.
      
      This patch contains the necessary common code changes to be able to
      distinguish idle system time and true idle time. The architectures with
      support for VIRT_CPU_ACCOUNTING need some changes to exploit this.
      Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
      79741dd3
    • M
      [PATCH] fix scaled & unscaled cputime accounting · 457533a7
      Martin Schwidefsky 提交于
      The utimescaled / stimescaled fields in the task structure and the
      global cpustat should be set on all architectures. On s390 the calls
      to account_user_time_scaled and account_system_time_scaled never have
      been added. In addition system time that is accounted as guest time
      to the user time of a process is accounted to the scaled system time
      instead of the scaled user time.
      To fix the bugs and to prevent future forgetfulness this patch merges
      account_system_time_scaled into account_system_time and
      account_user_time_scaled into account_user_time.
      
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
      Cc: Chris Wright <chrisw@sous-sol.org>
      Cc: Michael Neuling <mikey@neuling.org>
      Acked-by: NPaul Mackerras <paulus@samba.org>
      Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
      457533a7
  19. 13 12月, 2008 1 次提交
  20. 06 11月, 2008 2 次提交
    • P
      powerpc: Eliminate unused do_gtod variable · 3cc69878
      Paul Mackerras 提交于
      Since we started using the generic timekeeping code, we haven't had a
      powerpc-specific version of do_gettimeofday, and hence there is now
      nothing that reads the do_gtod variable in arch/powerpc/kernel/time.c.
      This therefore removes it and the code that sets it.
      Signed-off-by: NPaul Mackerras <paulus@samba.org>
      3cc69878
    • P
      powerpc: Improve resolution of VDSO clock_gettime · 597bc5c0
      Paul Mackerras 提交于
      Currently the clock_gettime implementation in the VDSO produces a
      result with microsecond resolution for the cases that are handled
      without a system call, i.e. CLOCK_REALTIME and CLOCK_MONOTONIC.  The
      nanoseconds field of the result is obtained by computing a
      microseconds value and multiplying by 1000.
      
      This changes the code in the VDSO to do the computation for
      clock_gettime with nanosecond resolution.  That means that the
      resolution of the result will ultimately depend on the timebase
      frequency.
      
      Because the timestamp in the VDSO datapage (stamp_xsec, the real time
      corresponding to the timebase count in tb_orig_stamp) is in units of
      2^-20 seconds, it doesn't have sufficient resolution for computing a
      result with nanosecond resolution.  Therefore this adds a copy of
      xtime to the VDSO datapage and updates it in update_gtod() along with
      the other time-related fields.
      Signed-off-by: NPaul Mackerras <paulus@samba.org>
      597bc5c0
  21. 14 7月, 2008 1 次提交
  22. 26 6月, 2008 1 次提交
  23. 14 5月, 2008 1 次提交
    • M
      [POWERPC] Fix sparse warnings in arch/powerpc/kernel · 1c21a293
      Michael Ellerman 提交于
      Make a few things static in lparcfg.c
      Make init and exit routines static in rtas_flash.c
      Make things static in rtas_pci.c
      Make some functions static in rtas.c
      Make fops static in rtas-proc.c
      Remove unneeded extern for do_gtod in smp.c
      Make clocksource_init() static in time.c
      Make last_tick_len and ticklen_to_xs static in time.c
      Move the declaration of the pvr per-cpu into smp.h
      Make kexec_smp_down() and kexec_stack static in machine_kexec_64.c
      Don't return void in arch_teardown_msi_irqs() in msi.c
      Move declaration of GregorianDay()into asm/time.h
      Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
      Signed-off-by: NPaul Mackerras <paulus@samba.org>
      1c21a293
  24. 01 5月, 2008 2 次提交
  25. 07 2月, 2008 1 次提交
    • M
      taskstats scaled time cleanup · 06b8e878
      Michael Neuling 提交于
      This moves the ability to scale cputime into generic code.  This allows us
      to fix the issue in kernel/timer.c (noticed by Balbir) where we could only
      add an unscaled value to the scaled utime/stime.
      
      This adds a cputime_to_scaled function.  As before, the POWERPC version
      does the scaling based on the last SPURR/PURR ratio calculated.  The
      generic and s390 (only other arch to implement asm/cputime.h) versions are
      both NOPs.
      
      Also moves the SPURR and PURR snapshots closer.
      Signed-off-by: NMichael Neuling <mikey@neuling.org>
      Cc: Jay Lan <jlan@engr.sgi.com>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      06b8e878
  26. 21 12月, 2007 1 次提交
    • S
      [POWERPC] Implement arch disable/enable irq hooks. · 7ac5dde9
      Scott Wood 提交于
      These hooks ensure that a decrementer interrupt is not pending when
      suspending; otherwise, problems may occur on 6xx/7xx/7xxx-based
      systems (except for powermacs, which use a separate suspend path).
      For example, with deep sleep on the 831x, a pending decrementer will
      cause a system freeze because the SoC thinks the decrementer interrupt
      would have woken the system, but the core must have interrupts
      disabled due to the setup required for deep sleep.
      
      Changed via-pmu.c to use the new ppc_md hooks, and made the arch_*
      functions call the generic_* functions unconditionally.  -- paulus
      Signed-off-by: NScott Wood <scottwood@freescale.com>
      Signed-off-by: NPaul Mackerras <paulus@samba.org>
      7ac5dde9
  27. 20 12月, 2007 5 次提交
  28. 20 11月, 2007 1 次提交
  29. 13 11月, 2007 1 次提交
  30. 10 11月, 2007 1 次提交
    • P
      sched: restore deterministic CPU accounting on powerpc · fa13a5a1
      Paul Mackerras 提交于
      Since powerpc started using CONFIG_GENERIC_CLOCKEVENTS, the
      deterministic CPU accounting (CONFIG_VIRT_CPU_ACCOUNTING) has been
      broken on powerpc, because we end up counting user time twice: once in
      timer_interrupt() and once in update_process_times().
      
      This fixes the problem by pulling the code in update_process_times
      that updates utime and stime into a separate function called
      account_process_tick.  If CONFIG_VIRT_CPU_ACCOUNTING is not defined,
      there is a version of account_process_tick in kernel/timer.c that
      simply accounts a whole tick to either utime or stime as before.  If
      CONFIG_VIRT_CPU_ACCOUNTING is defined, then arch code gets to
      implement account_process_tick.
      
      This also lets us simplify the s390 code a bit; it means that the s390
      timer interrupt can now call update_process_times even when
      CONFIG_VIRT_CPU_ACCOUNTING is turned on, and can just implement a
      suitable account_process_tick().
      
      account_process_tick() now takes the task_struct * as an argument.
      Tested both with and without CONFIG_VIRT_CPU_ACCOUNTING.
      Signed-off-by: NPaul Mackerras <paulus@samba.org>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      fa13a5a1
  31. 08 11月, 2007 1 次提交
    • P
      [POWERPC] Fix off-by-one error in setting decrementer on Book E/4xx (v2) · 43875cc0
      Paul Mackerras 提交于
      The decrementer in Book E and 4xx processors interrupts on the
      transition from 1 to 0, rather than on the 0 to -1 transition as on
      64-bit server and 32-bit "classic" (6xx/7xx/7xxx) processors.  At the
      moment we subtract 1 from the count of how many decrementer ticks are
      required before the next interrupt before putting it into the
      decrementer, which is correct for server/classic processors, but could
      possibly cause the interrupt to happen too early on Book E and 4xx if
      the timebase/decrementer frequency is low.
      
      This fixes the problem by making set_dec subtract 1 from the count for
      server and classic processors, instead of having the callers subtract
      1.  Since set_dec already had a bunch of ifdefs to handle different
      processor types, there is no net increase in ugliness. :)
      
      Note that calling set_dec(0) may not generate an interrupt on some
      processors.  To make sure that decrementer_set_next_event always calls
      set_dec with an interval of at least 1 tick, we set min_delta_ns of
      the decrementer_clockevent to correspond to 2 ticks (2 rather than 1
      to compensate for truncations in the conversions between ticks and
      ns).
      
      This also removes a redundant call to set the decrementer to
      0x7fffffff - it was already set to that earlier in timer_interrupt.
      Signed-off-by: NPaul Mackerras <paulus@samba.org>
      43875cc0
  32. 19 10月, 2007 1 次提交
    • M
      powerpc: add scaled time accounting · 4603ac18
      Michael Neuling 提交于
      This adds POWERPC specific hooks for scaled time accounting.
      
      POWER6 includes a SPURR register.  The SPURR is based off the PURR register
      but is scaled based on CPU frequency and issue rates.  This gives a more
      accurate account of the instructions used per task.  The PURR and timebase
      will be constant relative to the wall clock, irrespective of the CPU
      frequency.
      
      This implementation reads the SPURR register in account_system_vtime which
      is only call called on context witch and hard and soft irq entry and exit.
      The percentage of user and system time is then estimated using the ratio of
      these accounted by the PURR.  If the SPURR is not present, the PURR read.
      
      An earlier implementation of this patch read the SPURR whenever the PURR
      was read, which included the system call entry and exit path.
      Unfortunately this showed a performance regression on lmbench runs, so was
      re-implemented.
      
      I've included the lmbench results here when run bare metal on POWER6.  1st
      column is the unpatch results.  2nd column is the results using the below
      patch and the 3rd is the % diff of these results from the base.  4th and
      5th columns are the results and % differnce from the base using the older
      patch (SPURR read in syscall entry/exit path).
      
                                    Base        Scaled-Acct     SPURR-in-syscall
                                   Result      Result  % diff    Result % diff
      Simple syscall:              0.3086      0.3086  0.0000    0.3452 11.8600
      Simple read:                 0.4591      0.4671  1.7425    0.5044 9.86713
      Simple write:                0.4364      0.4366  0.0458    0.4731 8.40971
      Simple stat:                 2.0055      2.0295  1.1967    2.0669 3.06158
      Simple fstat:                0.5962      0.5876  -1.442    0.6368 6.80979
      Simple open/close:           3.1283      3.1009  -0.875    3.2088 2.57328
      Select on 10 fd's:           0.8554      0.8457  -1.133    0.8667 1.32101
      Select on 100 fd's:          3.5292      3.6329  2.9383    3.6664 3.88756
      Select on 250 fd's:          7.9097      8.1881  3.5197    8.2242 3.97613
      Select on 500 fd's:          15.2659     15.836  3.7357    15.873 3.97814
      Select on 10 tcp fd's:       0.9576      0.9416  -1.670    0.9752 1.83792
      Select on 100 tcp fd's:      7.248       7.2254  -0.311    7.2685 0.28283
      Select on 250 tcp fd's:      17.7742     17.707  -0.375    17.749 -0.1406
      Select on 500 tcp fd's:      35.4258     35.25   -0.496    35.286 -0.3929
      Signal handler installation: 0.6131      0.6075  -0.913    0.647  5.52927
      Signal handler overhead:     2.0919      2.1078  0.7600    2.1831 4.35967
      Protection fault:            0.7345      0.7478  1.8107    0.8031 9.33968
      Pipe latency:                33.006      16.398  -50.31    33.475 1.42368
      AF_UNIX sock stream latency: 14.5093     30.910  113.03    30.715 111.692
      Process fork+exit:           219.8       222.8   1.3648    229.37 4.35623
      Process fork+execve:         876.14      873.28  -0.32     868.66 -0.8533
      Process fork+/bin/sh -c:     2830        2876.5  1.6431    2958   4.52296
      File /var/tmp/XXX write bw:  1193497     1195536 0.1708    118657 -0.5799
      Pagefaults on /var/tmp/XXX:  3.1272      3.2117  2.7020    3.2521 3.99398
      
      Also, kernel compile times show no difference with this patch applied.
      
      [pbadari@us.ibm.com: Avoid unnecessary PURR reading]
      Signed-off-by: NMichael Neuling <mikey@neuling.org>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Cc: Jay Lan <jlan@engr.sgi.com>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Signed-off-by: NBadari Pulavarty <pbadari@us.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      4603ac18