linux.git/arch/powerpc/kernel/time.c, branch v2.6.39

powerpc: Fix oops if scan_dispatch_log is called too early

2011-04-18T03:08:19+00:00

We currently enable interrupts before the dispatch log for the boot
cpu is setup. If a timer interrupt comes in early enough we oops in
scan_dispatch_log:

Unable to handle kernel paging request for data at address 0x00000010

...

.scan_dispatch_log+0xb0/0x170
.account_system_vtime+0xa0/0x220
.irq_enter+0x88/0xc0
.do_IRQ+0x48/0x230

The patch below adds a check to scan_dispatch_log to ensure the
dispatch log has been allocated.

Signed-off-by: Anton Blanchard 
Cc: 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Make decrementer interrupt robust against offlined CPUs

2011-04-01T04:37:07+00:00

With some implementations, it is possible that a timer interrupt
occurs every few seconds on an offline CPU. In this case, just
re-arm the decrementer and return immediately

Signed-off-by: Benjamin Herrenschmidt

powerpc: Fix accounting of softirq time when idle

2011-03-29T23:44:18+00:00

commit cf9efce0ce31 (powerpc: Account time using timebase rather
than PURR) used in_irq() to detect if the time was spent in
interrupt processing. This only catches hardirq context so if we
are in softirq context and in the idle loop we end up accounting it
as idle time. If we instead use in_interrupt() we catch both softirq
and hardirq time.

The issue was found when running a network intensive workload. top
showed the following:

0.0%us,  1.1%sy,  0.0%ni, 85.7%id,  0.0%wa,  9.9%hi,  3.3%si,  0.0%st

85.7% idle. But this was wildly different to the perf events data.
To confirm the suspicion I ran something to keep the core busy:

# yes > /dev/null &

8.2%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa, 10.3%hi, 81.4%si,  0.0%st

We only got 8.2% of the CPU for the userspace task and softirq has
shot up to 81.4%.

With the patch below top shows the correct stats:

0.0%us,  0.0%sy,  0.0%ni,  5.3%id,  0.0%wa, 13.3%hi, 81.3%si,  0.0%st

Signed-off-by: Anton Blanchard 
Cc: stable@kernel.org
Signed-off-by: Benjamin Herrenschmidt

powerpc/cell: Use system_wq in cpufreq_spudemand

2011-01-21T03:08:34+00:00

With cmwq, there's no reason to use a separate workqueue in
cpufreq_spudemand.  Use system_wq instead.  The work items are already
sync canceled on stop, so it's already guaranteed that no work is
running when spu_gov_exit() is entered.

Signed-off-by: Tejun Heo 
Cc: Arnd Bergmann 
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Dave Jones 
Cc: cpufreq@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt

powerpc/time: printk time stamp init not correct

2010-12-09T04:35:31+00:00

problem:

I see sometimes on my mpc5200 based board such printk timing
information:

[    0.000000] NR_IRQS:512 nr_irqs:512 16
[    0.000000] MPC52xx PIC is up and running!
[    0.000000] clocksource: timebase mult[79364d9] shift[22] registered
[    0.000000] console [ttyPSC0] enabled
[  130.300633] pid_max: default: 32768 minimum: 301
[  130.305647] Mount-cache hash table entries: 512
[  130.315818] NET: Registered protocol family 16

reason:
if the tbu not starts from 0 when linux boots, boot_tb
maybe could not store the real 64 bit tbu value, because
boot_tp is only a 32 bit unsigned long.

solution:
change boot_tb to u64

[BenH: Made it u64 instead of unsigned long long]

Signed-off-by: Heiko Schocher 
cc: Wolfgang Denk 
Signed-off-by: Benjamin Herrenschmidt

Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc

2010-10-22T04:19:54+00:00

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc: (71 commits)
  powerpc/44x: Update ppc44x_defconfig
  powerpc/watchdog: Make default timeout for Book-E watchdog a Kconfig option
  fsl_rio: Add comments for sRIO registers.
  powerpc/fsl-booke: Add e55xx (64-bit) smp defconfig
  powerpc/fsl-booke: Add p5020 DS board support
  powerpc/fsl-booke64: Use TLB CAMs to cover linear mapping on FSL 64-bit chips
  powerpc/fsl-booke: Add support for FSL Arch v1.0 MMU in setup_page_sizes
  powerpc/fsl-booke: Add support for FSL 64-bit e5500 core
  powerpc/85xx: add cache-sram support
  powerpc/85xx: add ngPIXIS FPGA device tree node to the P1022DS board
  powerpc: Fix compile error with paca code on ppc64e
  powerpc/fsl-booke: Add p3041 DS board support
  oprofile/fsl emb: Don't set MSR[PMM] until after clearing the interrupt.
  powerpc/fsl-booke: Add PCI device ids for P2040/P3041/P5010/P5020 QoirQ chips
  powerpc/mpc8xxx_gpio: Add support for 'qoriq-gpio' controllers
  powerpc/fsl_booke: Add support to boot from core other than 0
  powerpc/p1022: Add probing for individual DMA channels
  powerpc/fsl_soc: Search all global-utilities nodes for rstccr
  powerpc: Fix invalid page flags in create TLB CAM path for PTE_64BIT
  powerpc/mpc83xx: Support for MPC8308 P1M board
  ...

Fix up conflict with the generic irq_work changes in arch/powerpc/kernel/time.c

irq_work: Add generic hardirq context callbacks

2010-10-18T17:58:50+00:00

Provide a mechanism that allows running code in IRQ context. It is
most useful for NMI code that needs to interact with the rest of the
system -- like wakeup a task to drain buffers.

Perf currently has such a mechanism, so extract that and provide it as
a generic feature, independent of perf so that others may also
benefit.

The IRQ context callback is generated through self-IPIs where
possible, or on architectures like powerpc the decrementer (the
built-in timer facility) is set to generate an interrupt immediately.

Architectures that don't have anything like this get to do with a
callback from the timer tick. These architectures can call
irq_work_run() at the tail of any IRQ handlers that might enqueue such
work (like the perf IRQ handler) to avoid undue latencies in
processing the work.

Signed-off-by: Peter Zijlstra 
Acked-by: Kyle McMartin 
Acked-by: Martin Schwidefsky 
[ various fixes ]
Signed-off-by: Huang Ying 
LKML-Reference: <1287036094.7768.291.camel@yhuang-dev>
Signed-off-by: Ingo Molnar

powerpc: export ppc_proc_freq and ppc_tb_freq as GPL symbols

2010-10-14T05:52:43+00:00

Export the global variable 'ppc_tb_freq', so that modules (like the Book-E
watchdog driver) can use it.  To maintain consistency, ppc_proc_freq is
changed to a GPL-only export.  This is okay, because any module that needs
this symbol should be an actual Linux driver, which must be GPL-licensed.

Signed-off-by: Timur Tabi 
Acked-by: Josh Boyer 
Signed-off-by: Kumar Gala

powerpc/pseries: Re-enable dispatch trace log userspace interface

2010-09-02T04:07:32+00:00

Since the cpu accounting code uses the hypervisor dispatch trace log
now when CONFIG_VIRT_CPU_ACCOUNTING = y, the previous commit disabled
access to it via files in the /sys/kernel/debug/powerpc/dtl/ directory
in that case.  This restores those files.

To do this, we now have a hook that the cpu accounting code will call
as it processes each entry from the hypervisor dispatch trace log.
The code in dtl.c now uses that to fill up its ring buffer, rather
than having the hypervisor fill the ring buffer directly.

This also fixes dtl_file_read() to handle overflow conditions a bit
better and adds a spinlock to ensure that race conditions (multiple
processes opening or reading the file concurrently) are handled
correctly.

Signed-off-by: Paul Mackerras 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Account time using timebase rather than PURR

2010-09-02T04:07:31+00:00

Currently, when CONFIG_VIRT_CPU_ACCOUNTING is enabled, we use the
PURR register for measuring the user and system time used by
processes, as well as other related times such as hardirq and
softirq times.  This turns out to be quite confusing for users
because it means that a program will often be measured as taking
less time when run on a multi-threaded processor (SMT2 or SMT4 mode)
than it does when run on a single-threaded processor (ST mode), even
though the program takes longer to finish.  The discrepancy is
accounted for as stolen time, which is also confusing, particularly
when there are no other partitions running.

This changes the accounting to use the timebase instead, meaning that
the reported user and system times are the actual number of real-time
seconds that the program was executing on the processor thread,
regardless of which SMT mode the processor is in.  Thus a program will
generally show greater user and system times when run on a
multi-threaded processor than on a single-threaded processor.

On pSeries systems on POWER5 or later processors, we measure the
stolen time (time when this partition wasn't running) using the
hypervisor dispatch trace log.  We check for new entries in the
log on every entry from user mode and on every transition from
kernel process context to soft or hard IRQ context (i.e. when
account_system_vtime() gets called).  So that we can correctly
distinguish time stolen from user time and time stolen from system
time, without having to check the log on every exit to user mode,
we store separate timestamps for exit to user mode and entry from
user mode.

On systems that have a SPURR (POWER6 and POWER7), we read the SPURR
in account_system_vtime() (as before), and then apportion the SPURR
ticks since the last time we read it between scaled user time and
scaled system time according to the relative proportions of user
time and system time over the same interval.  This avoids having to
read the SPURR on every kernel entry and exit.  On systems that have
PURR but not SPURR (i.e., POWER5), we do the same using the PURR
rather than the SPURR.

This disables the DTL user interface in /sys/debug/kernel/powerpc/dtl
for now since it conflicts with the use of the dispatch trace log
by the time accounting code.

Signed-off-by: Paul Mackerras 
Signed-off-by: Benjamin Herrenschmidt