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  1. 26 Feb, 2010 7 commits
    • Robert Richter's avatar
      oprofile/x86: implement randomization for IBS periodic op counter · ba52078e
      Robert Richter authored 
      IBS selects an op (execution operation) for sampling by counting
either cycles or dispatched ops. Better statistical samples can be
produced by adding a software generated random offset to the periodic
op counter value with each sample.

This patch adds software randomization to the IBS periodic op
counter. The lower 12 bits of the 20 bit counter are
randomized. IbsOpCurCnt is initialized with a 12 bit random value.

There is a work around if the hw can not write to IbsOpCurCnt. Then
the lower 8 bits of the 16 bit IbsOpMaxCnt [15:0] value are randomized
in the range of -128 to +127 by adding/subtracting an offset to the
maximum count (IbsOpMaxCnt).

The linear feedback shift register (LFSR) algorithm is used for
pseudo-random number generation to have low impact to the memory
system.
Signed-off-by: default avatarRobert Richter <robert.richter@amd.com>
      ba52078e
    • Suravee Suthikulpanit's avatar
      oprofile/x86: implement lsfr pseudo-random number generator for IBS · f125be14
      Suravee Suthikulpanit authored 
      This patch implements a linear feedback shift register (LFSR) for
pseudo-random number generation for IBS.

For IBS measurements it would be good to minimize memory traffic in
the interrupt handler since every access pollutes the data
caches. Computing a maximal period LFSR just needs shifts and ORs.

The LFSR method is good enough to randomize the ops at low
overhead. 16 pseudo-random bits are enough for the implementation and
it doesn't matter that the pattern repeats with a fairly short
cycle. It only needs to break up (hard) periodic sampling behavior.

The logic was designed by Paul Drongowski.
Signed-off-by: default avatarSuravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: default avatarRobert Richter <robert.richter@amd.com>
      f125be14
    • Robert Richter's avatar
      oprofile/x86: implement IBS cpuid feature detection · 64683da6
      Robert Richter authored 
      This patch adds IBS feature detection using cpuid flags. An IBS
capability mask is introduced to test for certain IBS features. The
bit mask is the same as for IBS cpuid feature flags (Fn8000_001B_EAX),
but bit 0 is used to indicate the existence of IBS.

The patch also changes the handling of the IbsOpCntCtl bit (periodic
op counter count control). The oprofilefs file for this feature
(ibs_op/dispatched_ops) will be only exposed if the feature is
available, also the default for the bit is set to count clock cycles.

In general, the userland can detect the availability of a feature by
checking for the corresponding file in oprofilefs. If it exists, the
feature also exists. This may lead to a dynamic file layout depending
on the cpu type with that the userland has to deal with. Current
opcontrol is compatible.
Signed-off-by: default avatarRobert Richter <robert.richter@amd.com>
      64683da6
    • Robert Richter's avatar
      oprofile/x86: remove node check in AMD IBS initialization · 89baaaa9
      Robert Richter authored 
      Standard AMD systems have the same number of nodes as there are
northbridge devices. However, there may kernel configurations
(especially for 32 bit) or system setups exist, where the node number
is different or it can not be detected properly. Thus the check is not
reliable and may fail though IBS setup was fine. For this reason it is
better to remove the check.

Cc: stable <stable@kernel.org>
Signed-off-by: default avatarRobert Richter <robert.richter@amd.com>
      89baaaa9
    • Robert Richter's avatar
      oprofile/x86: remove OPROFILE_IBS config option · 013cfc50
      Robert Richter authored 
      OProfile support for IBS is now for several versions in the
kernel. The feature is stable now and the code can be activated
permanently.

As a side effect IBS now works also on nosmp configs.
Signed-off-by: default avatarRobert Richter <robert.richter@amd.com>
      013cfc50
    • Robert Richter's avatar
      oprofile: remove EXPERIMENTAL from the config option description · b309a294
      Robert Richter authored 
      OProfile is already used for a long time and no longer experimental.
Signed-off-by: default avatarRobert Richter <robert.richter@amd.com>
      b309a294
    • Robert Richter's avatar
      oprofile: remove tracing build dependency · 18b4a4d5
      Robert Richter authored 
      The commit

 1155de47 ring-buffer: Make it generally available

already made ring-buffer available without the TRACING option
enabled. This patch removes the TRACING dependency from oprofile.

Fixes also oprofile configuration on ia64.

The patch also applies to the 2.6.32-stable kernel.
Reported-by: default avatarTony Jones <tonyj@suse.de>
Cc: stable@kernel.org
Signed-off-by: default avatarRobert Richter <robert.richter@amd.com>
      18b4a4d5
  3. 12 Feb, 2010 12 commits
  5. 11 Feb, 2010 21 commits
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