Per suggestion from Paul, move the event overflow bits to record_type
and sanitize the enums a bit.

Breaks the ABI -- again ;-)
Suggested-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Orig-LKML-Reference: <20090402091319.151921176@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Decouple kerneltop display from event acquisition by introducing
a separate data acquisition thread. This fixes annnoying kerneltop
display refresh jitter and missed events.

Also add a -r <prio> option, to switch the data acquisition thread
to real-time priority.
Signed-off-by: NMike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Follow the example set by powerpc and try to play nice with oprofile
and the nmi watchdog.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171024.459968444@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Provide the x86 perf_callchain() implementation.

Code based on the ftrace/sysprof code from Soeren Sandmann Pedersen.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Cc: Soeren Sandmann Pedersen <sandmann@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Orig-LKML-Reference: <20090330171024.341993293@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Provide the generic callchain support bits. If hw_event->callchain is
set the arch specific perf_callchain() function is called upon to
provide a perf_callchain_entry structure filled with the current
callchain.

If it does so, it is added to the overflow output event.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171024.254266860@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Go along with the new perf_event_type ABI.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171024.133985461@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Breaks ABI yet again :-)

Change the event type so that [0, 2^31-1] are regular event types, but
[2^31, 2^32-1] forms a bitmask for overflow events.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171024.047961770@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Move the nmi argument to the _begin() function, so that _end() only needs the
handle. This allows the _begin() function to generate a wakeup on event loss.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171023.959404268@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new functionality

This adds add an option to the perfstat mode of kerneltop to scale the
reported counter values according to the fraction of time that each
counter gets to count.  This is invoked with the -l option (I used 'l'
because s, c, a and e were all taken already.)  This uses the new
PERF_RECORD_TOTAL_TIME_{ENABLED,RUNNING} read format options.

With this, we get output like this:

$ ./perfstat -l -e 0:0,0:1,0:2,0:3,0:4,0:5 ./spin

 Performance counter stats for './spin':

     4016072055  CPU cycles           (events)  (scaled from 66.53%)
     2005887318  instructions         (events)  (scaled from 66.53%)
        1762849  cache references     (events)  (scaled from 66.69%)
         165229  cache misses         (events)  (scaled from 66.85%)
     1001298009  branches             (events)  (scaled from 66.78%)
          41566  branch misses        (events)  (scaled from 66.61%)

 Wall-clock time elapsed:  2438.227446 msecs

This also lets us detect when a counter is zero because the counter
never got to go on the CPU at all.  In that case we print <not counted>
rather than 0.
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <20090330171023.871484899@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Now that Paul cleaned up the error propagation paths, pass down the
x86 error as well.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171023.792822360@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: better error reporting

At present, if hw_perf_counter_init encounters an error, all it can do
is return NULL, which causes sys_perf_counter_open to return an EINVAL
error to userspace.  This isn't very informative for userspace; it means
that userspace can't tell the difference between "sorry, oprofile is
already using the PMU" and "we don't support this CPU" and "this CPU
doesn't support the requested generic hardware event".

This commit uses the PTR_ERR/ERR_PTR/IS_ERR set of macros to let
hw_perf_counter_init return an error code on error rather than just NULL
if it wishes.  If it does so, that error code will be returned from
sys_perf_counter_open to userspace.  If it returns NULL, an EINVAL
error will be returned to userspace, as before.

This also adapts the powerpc hw_perf_counter_init to make use of this
to return ENXIO, EINVAL, EBUSY, or EOPNOTSUPP as appropriate.  It would
be good to add extra error numbers in future to allow userspace to
distinguish the various errors that are currently reported as EINVAL,
i.e. irq_period < 0, too many events in a group, conflict between
exclude_* settings in a group, and PMU resource conflict in a group.

[ v2: fix a bug pointed out by Corey Ashford where error returns from
      hw_perf_counter_init were not handled correctly in the case of
      raw hardware events.]
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <20090330171023.682428180@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cooperate with oprofile

At present, on PowerPC, if you have perf_counters compiled in, oprofile
doesn't work.  There is code to allow the PMU to be shared between
competing subsystems, such as perf_counters and oprofile, but currently
the perf_counter subsystem reserves the PMU for itself at boot time,
and never releases it.

This makes perf_counter play nicely with oprofile.  Now we keep a count
of how many perf_counter instances are counting hardware events, and
reserve the PMU when that count becomes non-zero, and release the PMU
when that count becomes zero.  This means that it is possible to have
perf_counters compiled in and still use oprofile, as long as there are
no hardware perf_counters active.  This also means that if oprofile is
active, sys_perf_counter_open will fail if the hw_event specifies a
hardware event.

To avoid races with other tasks creating and destroying perf_counters,
we use a mutex.  We use atomic_inc_not_zero and atomic_add_unless to
avoid having to take the mutex unless there is a possibility of the
count going between 0 and 1.
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <20090330171023.627912475@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

frob the kerneltop code to print the mmap data in the stream

Better use would be collecting the IPs per PID and mapping them onto
the provided userspace code.. TODO
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171023.501902515@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Currently the profiling information returns userspace IPs but no way
to correlate them to userspace code. Userspace could look into
/proc/$pid/maps but that might not be current or even present anymore
at the time of analyzing the IPs.

Therefore provide means to track the mmap information and provide it
in the output stream.

XXX: only covers mmap()/munmap(), mremap() and mprotect() are missing.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Orig-LKML-Reference: <20090330171023.417259499@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Now that the kernel side changed, match up again.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171023.327144324@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

It just occured to me it is possible to have multiple contending
updates of the userpage (mmap information vs overflow vs counter).
This would break the seqlock logic.

It appear the arch code uses this from NMI context, so we cannot
possibly serialize its use, therefore separate the data_head update
from it and let it return to its original use.

The arch code needs to make sure there are no contending callers by
disabling the counter before using it -- powerpc appears to do this
nicely.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171023.241410660@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

While going over the wakeup code I noticed delayed wakeups only work
for hardware counters but basically all software counters rely on
them.

This patch unifies and generalizes the delayed wakeup to fix this
issue.

Since we're dealing with NMI context bits here, use a cmpxchg() based
single link list implementation to track counters that have pending
wakeups.

[ This should really be generic code for delayed wakeups, but since we
  cannot use cmpxchg()/xchg() in generic code, I've let it live in the
  perf_counter code. -- Eric Dumazet could use it to aggregate the
  network wakeups. ]

Furthermore, the x86 method of using TIF flags was flawed in that its
quite possible to end up setting the bit on the idle task, loosing the
wakeup.

The powerpc method uses per-cpu storage and does appear to be
sufficient.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171023.153932974@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new functionality

Currently, if there are more counters enabled than can fit on the CPU,
the kernel will multiplex the counters on to the hardware using
round-robin scheduling.  That isn't too bad for sampling counters, but
for counting counters it means that the value read from a counter
represents some unknown fraction of the true count of events that
occurred while the counter was enabled.

This remedies the situation by keeping track of how long each counter
is enabled for, and how long it is actually on the cpu and counting
events.  These times are recorded in nanoseconds using the task clock
for per-task counters and the cpu clock for per-cpu counters.

These values can be supplied to userspace on a read from the counter.
Userspace requests that they be supplied after the counter value by
setting the PERF_FORMAT_TOTAL_TIME_ENABLED and/or
PERF_FORMAT_TOTAL_TIME_RUNNING bits in the hw_event.read_format field
when creating the counter.  (There is no way to change the read format
after the counter is created, though it would be possible to add some
way to do that.)

Using this information it is possible for userspace to scale the count
it reads from the counter to get an estimate of the true count:

true_count_estimate = count * total_time_enabled / total_time_running

This also lets userspace detect the situation where the counter never
got to go on the cpu: total_time_running == 0.

This functionality has been requested by the PAPI developers, and will
be generally needed for interpreting the count values from counting
counters correctly.

In the implementation, this keeps 5 time values (in nanoseconds) for
each counter: total_time_enabled and total_time_running are used when
the counter is in state OFF or ERROR and for reporting back to
userspace.  When the counter is in state INACTIVE or ACTIVE, it is the
tstamp_enabled, tstamp_running and tstamp_stopped values that are
relevant, and total_time_enabled and total_time_running are determined
from them.  (tstamp_stopped is only used in INACTIVE state.)  The
reason for doing it like this is that it means that only counters
being enabled or disabled at sched-in and sched-out time need to be
updated.  There are no new loops that iterate over all counters to
update total_time_enabled or total_time_running.

This also keeps separate child_total_time_running and
child_total_time_enabled fields that get added in when reporting the
totals to userspace.  They are separate fields so that they can be
atomic.  We don't want to use atomics for total_time_running,
total_time_enabled etc., because then we would have to use atomic
sequences to update them, which are slower than regular arithmetic and
memory accesses.

It is possible to measure total_time_running by adding a task_clock
counter to each group of counters, and total_time_enabled can be
measured approximately with a top-level task_clock counter (though
inaccuracies will creep in if you need to disable and enable groups
since it is not possible in general to disable/enable the top-level
task_clock counter simultaneously with another group).  However, that
adds extra overhead - I measured around 15% increase in the context
switch latency reported by lat_ctx (from lmbench) when a task_clock
counter was added to each of 2 groups, and around 25% increase when a
task_clock counter was added to each of 4 groups.  (In both cases a
top-level task-clock counter was also added.)

In contrast, the code added in this commit gives better information
with no overhead that I could measure (in fact in some cases I
measured lower times with this code, but the differences were all less
than one standard deviation).

[ v2: address review comments by Andrew Morton. ]
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Orig-LKML-Reference: <18890.6578.728637.139402@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

A brainfart stopped single page mmap()s working. The rest of the code
should be perfectly fine with not having any data pages.
Reported-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <1237981712.7972.812.camel@twins>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Teach kerneltop about the new output ABI.

XXX: anybody fancy integrating the PID/TID data into the output?

Bump the mmap_data pages a little because we bloated the output and
have to be more careful about overruns with structured data.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Orig-LKML-Reference: <20090325113317.192910290@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

provide a knob to set the number of mmap data pages.
Signed-off-by: NMike Galbraith <efault@gmx.de>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Orig-LKML-Reference: <20090325113317.104545398@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Allow cpu wide counters to profile userspace by providing what process
the sample belongs to.

This raises the first issue with the output type, lots of these
options: group, tid, callchain, etc.. are non-exclusive and could be
combined, suggesting a bitfield.

However, things like the mmap() data stream doesn't fit in that.

How to split the type field...
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Orig-LKML-Reference: <20090325113317.013775235@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Ensure we never write more than we said we would.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Orig-LKML-Reference: <20090325113316.921433024@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Provide a {type,size} header for each output entry.

This should provide extensible output, and the ability to mix multiple streams.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Orig-LKML-Reference: <20090325113316.831607932@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Provide a begin, copy, end interface to the output buffer.

begin() reserves the space,
 copy() copies the data over, considering page boundaries,
  end() finalizes the event and does the wakeup.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Orig-LKML-Reference: <20090325113316.740550870@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix kerneltop 100% CPU usage

Only return a poll event when there's actually been one, poll_wait()
doesn't actually wait for the waitq you pass it, it only enqueues
you on it.

Only once all FDs have been iterated and none of thm returned a
poll-event will it schedule().

Also make it return POLL_HUP when there's not mmap() area to read from.

Further, fix a silly bug in the write code.
Reported-by: NMike Galbraith <efault@gmx.de>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Orig-LKML-Reference: <1237897096.24918.181.camel@twins>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: documentation fix

This updates the perfcounter documentation to reflect recent changes.
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Paul Mackerras wrote:

> I noticed the poll stuff is bogus - we have a 2D array of struct
> pollfds (MAX_NR_CPUS x MAX_COUNTERS), we fill in a sub-array (with the
> rest being uninitialized, since the array is on the stack) and then
> pass the first nr_cpus elements to poll.  Not what we really meant, I
> suspect. :)  Not even if we only have one counter, since it's the
> counter dimension that varies fastest.

This should fix the most obvious poll fubar.. not enough to fix the
full problem though..
Reported-by: NPaul Mackerras <paulus@samba.org>
Reported-by: NMike Galbraith <efault@gmx.de>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Orig-LKML-Reference: <18888.29986.340328.540512@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The glib dependency in kerneltop.c is only for a little bit of list
manipulation, and I find it inconvenient.  This adds a 'next' field to
struct source_line, which lets us link them together into a list.  The
code to do the linking ourselves turns out to be no longer or more
difficult than using glib.

This also fixes a few other problems:

- We need to #include <limits.h> to get PATH_MAX on powerpc.

- We need to #include <linux/types.h> rather than have our own
  definitions of __u64 and __s64; on powerpc the installed headers
  define them to be unsigned long and long respectively, and if we
  have our own, different definition here that causes a compile error.

- This takes out the x86 setting of errno from -ret in
  sys_perf_counter_open.  My experiments on x86 indicate that the
  glibc syscall() does this for us already.

- We had two CPU migration counters in the default set, which seems
  unnecessary; I changed one of them to a context switch counter.

- In perfstat mode we were printing CPU cycles and instructions as
  milliseconds, and the cpu clock and task clock counters as events.
  This fixes that.

- In perfstat mode we were still printing a blank line after the first
  counter, which was a holdover from when a task clock counter was
  automatically included as the first counter.  This removes the blank
  line.

- On a test machine here, parse_symbols() and parse_vmlinux() were
  taking long enough (almost 0.5 seconds) for the mmap buffer to
  overflow before we got to the first mmap_read() call, so this moves
  them before we open all the counters.

- The error message if sys_perf_counter_open fails needs to use errno,
  not -fd[i][counter].
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NMike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Orig-LKML-Reference: <18888.29986.340328.540512@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Commit b7368fdd7d decreased the CPU cycles interval 100-fold, but
this is causig kerneltop failures on my Nehalem box:

 aldebaran:/home/mingo/linux/linux/Documentation/perf_counter>
 ./kerneltop
 KernelTop refresh period: 2 seconds
 ERROR: failed to keep up with mmap data

10,000 cycles is way too short.

What we should do instead on mostly-idle systems is some sort of
read/poll timeout, so that we display something every 2 seconds
for sure.

Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Fix:

 kerneltop.c: In function ‘record_ip’:
 kerneltop.c:1005: warning: format ‘%016llx’ expects type ‘long long unsigned int’, but argument 2 has type ‘uint64_t’

Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <20090323172417.677932499@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Remove now unified perfstat.c and perf_counter.h, and link to the
in-kernel perf_counter.h.

Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <20090323172417.677932499@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

update kerneltop to use the mmap() output to gather overflow information
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090323172417.677932499@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

update the kerneltop userspace to work with the latest syscall ABI
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090323172417.559643732@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: Rework the perfcounter output ABI

use sys_read() only for instant data and provide mmap() output for all
async overflow data.

The first mmap() determines the size of the output buffer. The mmap()
size must be a PAGE_SIZE multiple of 1+pages, where pages must be a
power of 2 or 0. Further mmap()s of the same fd must have the same
size. Once all maps are gone, you can again mmap() with a new size.

In case of 0 extra pages there is no data output and the first page
only contains meta data.

When there are data pages, a poll() event will be generated for each
full page of data. Furthermore, the output is circular. This means
that although 1 page is a valid configuration, its useless, since
we'll start overwriting it the instant we report a full page.

Future work will focus on the output format (currently maintained)
where we'll likey want each entry denoted by a header which includes a
type and length.

Further future work will allow to splice() the fd, also containing the
async overflow data -- splice() would be mutually exclusive with
mmap() of the data.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090323172417.470536358@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: build fix

mutex_lock() is was defined inline in kernel/mutex.c, but wasn't
declared so not in <linux/mutex.h>.  This didn't cause a problem until
checkin 3a2d367d9aabac486ac4444c6c7ec7a1dab16267 added the
atomic_dec_and_mutex_lock() inline in between declaration and
definion.

This broke building with CONFIG_ALLOW_WARNINGS=n, e.g. make
allnoconfig.

Either from the source code nor the allnoconfig binary output I cannot
find any internal references to mutex_lock() in kernel/mutex.c, so
presumably this "inline" is now-useless legacy.

Cc: Eric Paris <eparis@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <tip-3a2d367d9aabac486ac4444c6c7ec7a1dab16267@git.kernel.org>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Much like the atomic_dec_and_lock() function in which we take an hold a
spin_lock if we drop the atomic to 0 this function takes and holds the
mutex if we dec the atomic to 0.
Signed-off-by: NEric Paris <eparis@redhat.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090323172417.410913479@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new feature giving performance improvement

This adds the ability for userspace to do an mmap on a hardware counter
fd and get access to a read-only page that contains the information
needed to translate a hardware counter value to the full 64-bit
counter value that would be returned by a read on the fd.  This is
useful on architectures that allow user programs to read the hardware
counters, such as PowerPC.

The mmap will only succeed if the counter is a hardware counter
monitoring the current process.

On my quad 2.5GHz PowerPC 970MP machine, userspace can read a counter
and translate it to the full 64-bit value in about 30ns using the
mmapped page, compared to about 830ns for the read syscall on the
counter, so this does give a significant performance improvement.
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <20090323172417.297057964@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Tracepoint events like lock_acquire and software counters like
pagefaults can recurse into the perf counter code again, avoid that.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090323172417.152096433@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Since the bitfields turned into a bit of a mess, remove them and rely on
good old masks.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090323172417.059499915@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>