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Jin Yao a3366db06b perf report: Fix wrong iteration count in --branch-history
By calculating the removed loops, we can get the iteration count.

But the iteration count could be reported incorrectly, reporting
impossibly high counts.

That's because previous code uses the number of removed LBR entries for
the iteration count. That's not good. Fix this by increasing the
iteration count when a loop is detected.

When matching the chain, the iteration count would be added up, finally we need
to compute the average value when printing out.

For example,

  $ perf report --branch-history --stdio --no-children

Before:

  ---f2 +0
     |
     |--33.62%--f1 +9 (cycles:1)
     |          f1 +0
     |          main +22 (cycles:1)
     |          main +17
     |          main +38 (cycles:1)
     |          main +27
     |          f1 +26 (cycles:1)
     |          f1 +24
     |          f2 +27 (cycles:7)
     |          f2 +0
     |          f1 +19 (cycles:1)
     |          f1 +14
     |          f2 +27 (cycles:11)
     |          f2 +0
     |          f1 +9 (cycles:1 iter:2968 avg_cycles:3)
     |          f1 +0
     |          main +22 (cycles:1 iter:2968 avg_cycles:3)
     |          main +17
     |          main +38 (cycles:1 iter:2968 avg_cycles:3)

2968 is an impossible high iteration count and avg_cycles is too small.

After:

  ---f2 +0
     |
     |--33.62%--f1 +9 (cycles:1)
     |          f1 +0
     |          main +22 (cycles:1)
     |          main +17
     |          main +38 (cycles:1)
     |          main +27
     |          f1 +26 (cycles:1)
     |          f1 +24
     |          f2 +27 (cycles:7)
     |          f2 +0
     |          f1 +19 (cycles:1)
     |          f1 +14
     |          f2 +27 (cycles:11)
     |          f2 +0
     |          f1 +9 (cycles:1 iter:1 avg_cycles:23)
     |          f1 +0
     |          main +22 (cycles:1 iter:1 avg_cycles:23)
     |          main +17
     |          main +38 (cycles:1 iter:1 avg_cycles:23)

avg_cycles:23 is the average cycles of this iteration.

Fixes: c4ee06251d ("perf report: Calculate the average cycles of iterations")

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1546582230-17507-1-git-send-email-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2019-01-04 12:54:49 -03:00
arch Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 18:42:51 -08:00
block
certs
crypto Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 13:07:19 -08:00
Documentation Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 13:07:19 -08:00
drivers Merge branch 'x86-amd-nb-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 16:12:50 -08:00
firmware
fs Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 13:07:19 -08:00
include Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 18:08:18 -08:00
init Merge branch 'efi-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 13:38:38 -08:00
ipc
kernel sched/fair: Fix warning on non-SMP build 2018-12-27 10:40:15 -08:00
lib Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 13:07:19 -08:00
LICENSES
mm Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 13:07:19 -08:00
net Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 13:07:19 -08:00
samples
scripts Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 13:07:19 -08:00
security
sound xen: features and fixes for 4.21 2018-12-26 11:35:07 -08:00
tools perf report: Fix wrong iteration count in --branch-history 2019-01-04 12:54:49 -03:00
usr
virt Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 13:07:19 -08:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 13:07:19 -08:00
Makefile
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.