This implements accurate task and cpu time accounting for 64-bit
powerpc kernels. Instead of accounting a whole jiffy of time to a
task on a timer interrupt because that task happened to be running at
the time, we now account time in units of timebase ticks according to
the actual time spent by the task in user mode and kernel mode. We
also count the time spent processing hardware and software interrupts
accurately. This is conditional on CONFIG_VIRT_CPU_ACCOUNTING. If
that is not set, we do tick-based approximate accounting as before.
To get this accurate information, we read either the PURR (processor
utilization of resources register) on POWER5 machines, or the timebase
on other machines on
* each entry to the kernel from usermode
* each exit to usermode
* transitions between process context, hard irq context and soft irq
context in kernel mode
* context switches.
On POWER5 systems with shared-processor logical partitioning we also
read both the PURR and the timebase at each timer interrupt and
context switch in order to determine how much time has been taken by
the hypervisor to run other partitions ("steal" time). Unfortunately,
since we need values of the PURR on both threads at the same time to
accurately calculate the steal time, and since we can only calculate
steal time on a per-core basis, the apportioning of the steal time
between idle time (time which we ceded to the hypervisor in the idle
loop) and actual stolen time is somewhat approximate at the moment.
This is all based quite heavily on what s390 does, and it uses the
generic interfaces that were added by the s390 developers,
i.e. account_system_time(), account_user_time(), etc.
This patch doesn't add any new interfaces between the kernel and
userspace, and doesn't change the units in which time is reported to
userspace by things such as /proc/stat, /proc/<pid>/stat, getrusage(),
times(), etc. Internally the various task and cpu times are stored in
timebase units, but they are converted to USER_HZ units (1/100th of a
second) when reported to userspace. Some precision is therefore lost
but there should not be any accumulating error, since the internal
accumulation is at full precision.
Signed-off-by: Paul Mackerras <paulus@samba.org>
At present the lppaca - the structure shared with the iSeries
hypervisor and phyp - is contained within the PACA, our own low-level
per-cpu structure. This doesn't have to be so, the patch below
removes it, making a separate array of lppaca structures.
This saves approximately 500*NR_CPUS bytes of image size and kernel
memory, because we don't need aligning gap between the Linux and
hypervisor portions of every PACA. On the other hand it means an
extra level of dereference in many accesses to the lppaca.
The patch also gets rid of several places where we assign the paca
address to a local variable for no particular reason.
Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
The 601 doesn't have the timebase register; instead it has an RTCL
register that counts nanoseconds and wraps at 1000000000, and an
RTCU register that counts seconds. This makes the necessary changes
for the merged time code to use the RTCL/U registers when the kernel
is running on a 601.
Signed-off-by: Paul Mackerras <paulus@samba.org>
This moves smp_space_timers from arch/ppc64/kernel/smp.c to
arch/powerpc/kernel/time.c and makes it initialize last_jiffy[]
instead of paca[].next_jiffy_update_tb, since last_jiffy[] is
now what the time code uses. It also declares smp_space_timers
in include/asm-powerpc/time.h and gets rid of an ifdef in
div128_by_32.
Signed-off-by: Paul Mackerras <paulus@samba.org>
I had the sense of the test for when to use the old 601-style RTC
registers inverted. pmac_calibrate_decr and via_calibrate_decr
weren't setting ppc_tb_freq, on which all the further calculations
depended. Lastly, update_gtod was losing the top 32 bits of
the new tb_to_xs value.
Signed-off-by: Paul Mackerras <paulus@samba.org>
We now use the merged time.c for both 32-bit and 64-bit compilation
with ARCH=powerpc, and for ARCH=ppc64, but not for ARCH=ppc32.
This removes setup_default_decr (folds its function into time_init)
and moves wakeup_decrementer into time.c. This also makes an
asm-powerpc/rtc.h.
Signed-off-by: Paul Mackerras <paulus@samba.org>
