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__get_cpu_var() is used for multiple purposes in the kernel source. One of
them is address calculation via the form &__get_cpu_var(x). This calculates
the address for the instance of the percpu variable of the current processor
based on an offset.
Other use cases are for storing and retrieving data from the current
processors percpu area. __get_cpu_var() can be used as an lvalue when
writing data or on the right side of an assignment.
__get_cpu_var() is defined as :
#define __get_cpu_var(var) (*this_cpu_ptr(&(var)))
__get_cpu_var() always only does an address determination. However, store
and retrieve operations could use a segment prefix (or global register on
other platforms) to avoid the address calculation.
this_cpu_write() and this_cpu_read() can directly take an offset into a
percpu area and use optimized assembly code to read and write per cpu
variables.
This patch converts __get_cpu_var into either an explicit address
calculation using this_cpu_ptr() or into a use of this_cpu operations that
use the offset. Thereby address calculations are avoided and less registers
are used when code is generated.
At the end of the patch set all uses of __get_cpu_var have been removed so
the macro is removed too.
The patch set includes passes over all arches as well. Once these operations
are used throughout then specialized macros can be defined in non -x86
arches as well in order to optimize per cpu access by f.e. using a global
register that may be set to the per cpu base.
Transformations done to __get_cpu_var()
1. Determine the address of the percpu instance of the current processor.
DEFINE_PER_CPU(int, y);
int *x = &__get_cpu_var(y);
Converts to
int *x = this_cpu_ptr(&y);
2. Same as #1 but this time an array structure is involved.
DEFINE_PER_CPU(int, y[20]);
int *x = __get_cpu_var(y);
Converts to
int *x = this_cpu_ptr(y);
3. Retrieve the content of the current processors instance of a per cpu
variable.
DEFINE_PER_CPU(int, y);
int x = __get_cpu_var(y)
Converts to
int x = __this_cpu_read(y);
4. Retrieve the content of a percpu struct
DEFINE_PER_CPU(struct mystruct, y);
struct mystruct x = __get_cpu_var(y);
Converts to
memcpy(&x, this_cpu_ptr(&y), sizeof(x));
5. Assignment to a per cpu variable
DEFINE_PER_CPU(int, y)
__get_cpu_var(y) = x;
Converts to
this_cpu_write(y, x);
6. Increment/Decrement etc of a per cpu variable
DEFINE_PER_CPU(int, y);
__get_cpu_var(y)++
Converts to
this_cpu_inc(y)
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
CC: linux390@de.ibm.com
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Use the new defines for external interruption codes to get rid
of "magic" numbers in the s390 source code. And while we're at it,
also rename the (un-)register_external_interrupt function to
something shorter so that this patch does not exceed the 80
columns all over the place.
Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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The patch "s390/perf: add support for the CPU-Measurement Sampling
Facility" added a new instance of the __cpuinit macro usage.
We removed this a couple versions ago; we now want to remove
the compat no-op stubs. Introducing new users is not what
we want to see at this point in time, as it will break once
the stubs are gone.
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Add the PERF_CPUM_SF_FULL_BLOCKS flag to process only sample-data-blocks that
have the block-full-indicator bit set. Sample-data-blocks that are partially
filled are discarded. Use this flag if the sampling buffer is likely to be
shared among perf events that use different sampling modes. In such
environments, flushing sample-data-blocks that are not completely filled, might
cause invalid-data-formats.
Setting PERF_CPUM_SF_FULL_BLOCKS prevents potentially invalid sampling data to
be processed but, in contrast, also discards valid samples in partially filled
sample-data-blocks. Note that sample-data-blocks might not become full for
small sampling frequencies or for workload that is scheduled for tiny intervals.
To sample with the PERF_CPUM_SF_FULL_BLOCKS flag, set the perf->attr.config1
to 0x0004. For example:
perf record -e cpum_sf/config=0xB000,config1=0x0004/
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Also support the diagnostic-sampling function in addition to the basic-sampling
function. Diagnostic-sampling data entries contain hardware model specific
sampling data and additional programs are required to analyze the data.
To deliver diagnostic-sampling, as well, as basis-sampling data entries to user
space, introduce support for sampling "raw data". If this particular perf
sampling type (PERF_SAMPLE_RAW) is used, sampling data entries are copied
to user space. External programs can then analyze these data.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Introduce the perf_exclude_event() function to filter perf samples
according to event->attr.exclude_* settings. During event initialization,
reset event exclude settings that are not supported.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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The host-program-parameter (hpp) value of basic sample-data-entries designates
a SIE control block that is set by the LPP instruction in sie64a().
Non-zero values indicate guest samples, a value of zero indicates a host sample.
For perf samples, host and guest samples are distinguished using particular
PERF_MISC_* flags. The perf layer calls perf_misc_flags() to set the flags
based on the pt_regs content. For each sample-data-entry, the cpum_sf PMU
creates a pt_regs structure with the sample-data information. An additional
flag structure is added to easily distinguish between host and guest samples.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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The trailer entry contains a timestamp of the time when the sample-data-block
became full. The timestamp specifies a TOD (time-of-day) value in either the
STCK or STCKE format.
Provide a helper function to return the TOD value depending on the setting of
time format indicator.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Ensure to reset the sample-data-block full indicator and the overflow counter
at the same time. This must be done atomically because the sampling hardware
is still active while full sample-data-block is processed.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Improve the sampling buffer allocation and add a function to reallocate and
increase the sampling buffer structure. The number of allocated buffer elements
(sample-data-blocks) are accounted. You can control the minimum and maximum
number these sample-data-blocks through the cpum_sfb_size kernel parameter.
The number hardware sample overflows (if any) are also accounted and stored
per perf event. During the PMU disable/enable calls, the accumulated overflow
counter is analyzed and, if necessary, the sampling buffer is dynamically
increased.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Introduce reserve/release functions to share the sampling facility
between perf and oprofile.
Also improve error handling for the sampling facility support in perf.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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The cpum_cf (counter facility) PMU does not support sampling events.
With cpum_sf (sampling facility), a PMU for sampling CPU cycles is
available.
Make cpum_sf the "default" PMU for PERF_COUNT_HW_CPU_CYCLES sampling
events but use the more precise cpum_cf PMU for non-sampling events.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Introduce a perf PMU, "cpum_sf", to support the CPU-Measurement
Sampling Facility. You can control the sampling facility through
this perf PMU interfaces. Perf sampling events are created for
hardware samples.
For details about the CPU-Measurement Sampling Facility, see
"The Load-Program-Parameter and the CPU-Measurement Facilities" (SA23-2260).
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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