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  1. 24 5月, 2009 1 次提交
    • P
      perf_counter: Fix dynamic irq_period logging · e220d2dc
      由 Peter Zijlstra 提交于 
      We call perf_adjust_freq() from perf_counter_task_tick() which
is is called under the rq->lock causing lock recursion.
However, it's no longer required to be called under the
rq->lock, so remove it from under it.

Also, fix up some related comments.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090523163012.476197912@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      e220d2dc
  3. 22 5月, 2009 3 次提交
    • I
      perf_counter: fix !PERF_COUNTERS build failure · 910431c7
      由 Ingo Molnar 提交于 
      Update the !CONFIG_PERF_COUNTERS prototype too, for
perf_counter_task_sched_out().

[ Impact: build fix ]
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <18966.10666.517218.332164@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      910431c7
    • P
      perf_counter: Optimize context switch between identical inherited contexts · 564c2b21
      由 Paul Mackerras 提交于 
      When monitoring a process and its descendants with a set of inherited
counters, we can often get the situation in a context switch where
both the old (outgoing) and new (incoming) process have the same set
of counters, and their values are ultimately going to be added together.
In that situation it doesn't matter which set of counters are used to
count the activity for the new process, so there is really no need to
go through the process of reading the hardware counters and updating
the old task's counters and then setting up the PMU for the new task.

This optimizes the context switch in this situation.  Instead of
scheduling out the perf_counter_context for the old task and
scheduling in the new context, we simply transfer the old context
to the new task and keep using it without interruption.  The new
context gets transferred to the old task.  This means that both
tasks still have a valid perf_counter_context, so no special case
is introduced when the old task gets scheduled in again, either on
this CPU or another CPU.

The equivalence of contexts is detected by keeping a pointer in
each cloned context pointing to the context it was cloned from.
To cope with the situation where a context is changed by adding
or removing counters after it has been cloned, we also keep a
generation number on each context which is incremented every time
a context is changed.  When a context is cloned we take a copy
of the parent's generation number, and two cloned contexts are
equivalent only if they have the same parent and the same
generation number.  In order that the parent context pointer
remains valid (and is not reused), we increment the parent
context's reference count for each context cloned from it.

Since we don't have individual fds for the counters in a cloned
context, the only thing that can make two clones of a given parent
different after they have been cloned is enabling or disabling all
counters with prctl.  To account for this, we keep a count of the
number of enabled counters in each context.  Two contexts must have
the same number of enabled counters to be considered equivalent.

Here are some measurements of the context switch time as measured with
the lat_ctx benchmark from lmbench, comparing the times obtained with
and without this patch series:

		-----Unmodified-----		With this patch series
Counters:	none	2 HW	4H+4S	none	2 HW	4H+4S

2 processes:
Average		3.44	6.45	11.24	3.12	3.39	3.60
St dev		0.04	0.04	0.13	0.05	0.17	0.19

8 processes:
Average		6.45	8.79	14.00	5.57	6.23	7.57
St dev		1.27	1.04	0.88	1.42	1.46	1.42

32 processes:
Average		5.56	8.43	13.78	5.28	5.55	7.15
St dev		0.41	0.47	0.53	0.54	0.57	0.81

The numbers are the mean and standard deviation of 20 runs of
lat_ctx.  The "none" columns are lat_ctx run directly without any
counters.  The "2 HW" columns are with lat_ctx run under perfstat,
counting cycles and instructions.  The "4H+4S" columns are lat_ctx run
under perfstat with 4 hardware counters and 4 software counters
(cycles, instructions, cache references, cache misses, task
clock, context switch, cpu migrations, and page faults).

[ Impact: performance optimization of counter context-switches ]
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <18966.10666.517218.332164@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      564c2b21
    • P
      perf_counter: Dynamically allocate tasks' perf_counter_context struct · a63eaf34
      由 Paul Mackerras 提交于 
      This replaces the struct perf_counter_context in the task_struct with
a pointer to a dynamically allocated perf_counter_context struct.  The
main reason for doing is this is to allow us to transfer a
perf_counter_context from one task to another when we do lazy PMU
switching in a later patch.

This has a few side-benefits: the task_struct becomes a little smaller,
we save some memory because only tasks that have perf_counters attached
get a perf_counter_context allocated for them, and we can remove the
inclusion of <linux/perf_counter.h> in sched.h, meaning that we don't
end up recompiling nearly everything whenever perf_counter.h changes.

The perf_counter_context structures are reference-counted and freed
when the last reference is dropped.  A context can have references
from its task and the counters on its task.  Counters can outlive the
task so it is possible that a context will be freed well after its
task has exited.

Contexts are allocated on fork if the parent had a context, or
otherwise the first time that a per-task counter is created on a task.
In the latter case, we set the context pointer in the task struct
locklessly using an atomic compare-and-exchange operation in case we
raced with some other task in creating a context for the subject task.

This also removes the task pointer from the perf_counter struct.  The
task pointer was not used anywhere and would make it harder to move a
context from one task to another.  Anything that needed to know which
task a counter was attached to was already using counter->ctx->task.

The __perf_counter_init_context function moves up in perf_counter.c
so that it can be called from find_get_context, and now initializes
the refcount, but is otherwise unchanged.

We were potentially calling list_del_counter twice: once from
__perf_counter_exit_task when the task exits and once from
__perf_counter_remove_from_context when the counter's fd gets closed.
This adds a check in list_del_counter so it doesn't do anything if
the counter has already been removed from the lists.

Since perf_counter_task_sched_in doesn't do anything if the task doesn't
have a context, and leaves cpuctx->task_ctx = NULL, this adds code to
__perf_install_in_context to set cpuctx->task_ctx if necessary, i.e. in
the case where the current task adds the first counter to itself and
thus creates a context for itself.

This also adds similar code to __perf_counter_enable to handle a
similar situation which can arise when the counters have been disabled
using prctl; that also leaves cpuctx->task_ctx = NULL.

[ Impact: refactor counter context management to prepare for new feature ]
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <18966.10075.781053.231153@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      a63eaf34
  5. 20 5月, 2009 3 次提交
    • P
      perf_counter: Log irq_period changes · 26b119bc
      由 Peter Zijlstra 提交于 
      For the dynamic irq_period code, log whenever we change the period so that
analyzing code can normalize the event flow.

[ Impact: add new feature to allow more precise profiling ]
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090520102553.298769743@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      26b119bc
    • P
      perf_counter: Solve the rotate_ctx vs inherit race differently · d7b629a3
      由 Peter Zijlstra 提交于 
      Instead of disabling RR scheduling of the counters, use a different list
that does not get rotated to iterate the counters on inheritance.

[ Impact: cleanup, optimization ]
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090520102553.237504544@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      d7b629a3
    • I
      perf_counter: fix counter inheritance race · c44d70a3
      由 Ingo Molnar 提交于 
      Context rotation should not occur when we are in the middle of
walking the counter list when inheriting counters ...

[ Impact: fix occasionally incorrect perf stat results ]

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      c44d70a3
  7. 15 5月, 2009 3 次提交
    • P
      perf_counter: allow arch to supply event misc flags and instruction pointer · 9d23a90a
      由 Paul Mackerras 提交于 
      At present the values we put in overflow events for the misc
flags indicating processor mode and the instruction pointer are
obtained using the standard user_mode() and
instruction_pointer() functions. Those functions tell you where
the performance monitor interrupt was taken, which might not be
exactly where the counter overflow occurred, for example
because interrupts were disabled at the point where the
overflow occurred, or because the processor had many
instructions in flight and chose to complete some more
instructions beyond the one that caused the counter overflow.

Some architectures (e.g. powerpc) can supply more precise
information about where the counter overflow occurred and the
processor mode at that point.  This introduces new functions,
perf_misc_flags() and perf_instruction_pointer(), which arch
code can override to provide more precise information if
available.  They have default implementations which are
identical to the existing code.

This also adds a new misc flag value,
PERF_EVENT_MISC_HYPERVISOR, for the case where a counter
overflow occurred in the hypervisor.  We encode the processor
mode in the 2 bits previously used to indicate user or kernel
mode; the values for user and kernel mode are unchanged and
hypervisor mode is indicated by both bits being set.

[ Impact: generalize perfcounter core facilities ]
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <18956.1272.818511.561835@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      9d23a90a
    • P
      perf_counter: frequency based adaptive irq_period · 60db5e09
      由 Peter Zijlstra 提交于 
      Instead of specifying the irq_period for a counter, provide a target interrupt
frequency and dynamically adapt the irq_period to match this frequency.

[ Impact: new perf-counter attribute/feature ]
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <20090515132018.646195868@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      60db5e09
    • P
      perf_counter: Rework the perf counter disable/enable · 9e35ad38
      由 Peter Zijlstra 提交于 
      The current disable/enable mechanism is:

	token = hw_perf_save_disable();
	...
	/* do bits */
	...
	hw_perf_restore(token);

This works well, provided that the use nests properly. Except we don't.

x86 NMI/INT throttling has non-nested use of this, breaking things. Therefore
provide a reference counter disable/enable interface, where the first disable
disables the hardware, and the last enable enables the hardware again.

[ Impact: refactor, simplify the PMU disable/enable logic ]
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      9e35ad38
  9. 09 5月, 2009 3 次提交
    • P
      perf_counter: add PERF_RECORD_CPU · f370e1e2
      由 Peter Zijlstra 提交于 
      Allow recording the CPU number the event was generated on.

RFC: this leaves a u32 as reserved, should we fill in the
     node_id() there, or leave this open for future extention,
     as userspace can already easily do the cpu->node mapping
     if needed.

[ Impact: extend perfcounter output record format ]
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090508170029.008627711@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      f370e1e2
    • P
      perf_counter: add PERF_RECORD_CONFIG · a85f61ab
      由 Peter Zijlstra 提交于 
      Much like CONFIG_RECORD_GROUP records the hw_event.config to
identify the values, allow to record this for all counters.

[ Impact: extend perfcounter output record format ]
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090508170028.923228280@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      a85f61ab
    • P
      perf_counter: rework ioctl()s · 3df5edad
      由 Peter Zijlstra 提交于 
      Corey noticed that ioctl()s on grouped counters didn't work on
the whole group. This extends the ioctl() interface to take a
second argument that is interpreted as a flags field. We then
provide PERF_IOC_FLAG_GROUP to toggle the behaviour.

Having this flag gives the greatest flexibility, allowing you
to individually enable/disable/reset counters in a group, or
all together.

[ Impact: fix group counter enable/disable semantics ]
Reported-by: NCorey Ashford <cjashfor@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20090508170028.837558214@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      3df5edad
  11. 06 5月, 2009 3 次提交
  13. 05 5月, 2009 1 次提交
    • I
      perf_counter: initialize the per-cpu context earlier · 0d905bca
      由 Ingo Molnar 提交于 
      percpu scheduling for perfcounters wants to take the context lock,
but that lock first needs to be initialized. Currently it is an
early_initcall() - but that is too late, the task tick runs much
sooner than that.

Call it explicitly from the scheduler init sequence instead.

[ Impact: fix access-before-init crash ]

LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      0d905bca
  15. 01 5月, 2009 1 次提交
    • P
      perf_counter: fix race in perf_output_* · c33a0bc4
      由 Peter Zijlstra 提交于 
      When two (or more) contexts output to the same buffer, it is possible
to observe half written output.

Suppose we have CPU0 doing perf_counter_mmap(), CPU1 doing
perf_counter_overflow(). If CPU1 does a wakeup and exposes head to
user-space, then CPU2 can observe the data CPU0 is still writing.

[ Impact: fix occasionally corrupted profiling records ]
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090501102533.007821627@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      c33a0bc4
  17. 29 4月, 2009 3 次提交
  19. 09 4月, 2009 7 次提交
  21. 07 4月, 2009 10 次提交
  23. 06 4月, 2009 2 次提交