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052747700e
With the existing symbol_from/symbol_to, branches captured in the same
function would be collapsed into a single function if the latencies
associated with the each branch (cycles) were all the same. That is the
case on Intel Broadwell, for instance. Since Intel Skylake, the latency
is captured by hardware and therefore is used to disambiguate branches.
Add addr_from/addr_to sort dimensions to sort branches based on their
addresses and not the function there are in. The output is still the
function name but the offset within the function is provided to uniquely
identify each branch. These new sort dimensions also help with annotate
because they create different entries in the histogram which, in turn,
generates proper branch annotations.
Here is an example using AMD's branch sampling:
$ perf record -a -b -c 1000037 -e cpu/branch-brs/ test_prg
$ perf report
Samples: 6M of event 'cpu/branch-brs/', Event count (approx.): 6901276
Overhead Command Source Shared Object Source Symbol Target Symbol Basic Block Cycle
99.65% test_prg test_prg [.] test_thread [.] test_thread -
0.02% test_prg [kernel.vmlinux] [k] asm_sysvec_apic_timer_interrupt [k] error_entry -
$ perf report -F overhead,comm,dso,addr_from,addr_to
Samples: 6M of event 'cpu/branch-brs/', Event count (approx.): 6901276
Overhead Command Shared Object Source Address Target Address
4.22% test_prg test_prg [.] test_thread+0x3c [.] test_thread+0x4
4.13% test_prg test_prg [.] test_thread+0x4 [.] test_thread+0x3a
4.09% test_prg test_prg [.] test_thread+0x3a [.] test_thread+0x6
4.08% test_prg test_prg [.] test_thread+0x2 [.] test_thread+0x3c
4.06% test_prg test_prg [.] test_thread+0x3e [.] test_thread+0x2
3.87% test_prg test_prg [.] test_thread+0x6 [.] test_thread+0x38
3.84% test_prg test_prg [.] test_thread [.] test_thread+0x3e
3.76% test_prg test_prg [.] test_thread+0x1e [.] test_thread
3.76% test_prg test_prg [.] test_thread+0x38 [.] test_thread+0x8
3.56% test_prg test_prg [.] test_thread+0x22 [.] test_thread+0x1e
3.54% test_prg test_prg [.] test_thread+0x8 [.] test_thread+0x36
3.47% test_prg test_prg [.] test_thread+0x1c [.] test_thread+0x22
3.45% test_prg test_prg [.] test_thread+0x36 [.] test_thread+0xa
3.28% test_prg test_prg [.] test_thread+0x24 [.] test_thread+0x1c
3.25% test_prg test_prg [.] test_thread+0xa [.] test_thread+0x34
3.24% test_prg test_prg [.] test_thread+0x1a [.] test_thread+0x24
3.20% test_prg test_prg [.] test_thread+0x34 [.] test_thread+0xc
3.04% test_prg test_prg [.] test_thread+0x26 [.] test_thread+0x1a
3.01% test_prg test_prg [.] test_thread+0xc [.] test_thread+0x32
2.98% test_prg test_prg [.] test_thread+0x18 [.] test_thread+0x26
2.94% test_prg test_prg [.] test_thread+0x32 [.] test_thread+0xe
2.76% test_prg test_prg [.] test_thread+0x28 [.] test_thread+0x18
2.73% test_prg test_prg [.] test_thread+0xe [.] test_thread+0x30
2.67% test_prg test_prg [.] test_thread+0x30 [.] test_thread+0x10
2.67% test_prg test_prg [.] test_thread+0x16 [.] test_thread+0x28
2.46% test_prg test_prg [.] test_thread+0x10 [.] test_thread+0x2e
2.44% test_prg test_prg [.] test_thread+0x2a [.] test_thread+0x16
2.38% test_prg test_prg [.] test_thread+0x14 [.] test_thread+0x2a
2.32% test_prg test_prg [.] test_thread+0x2e [.] test_thread+0x12
2.28% test_prg test_prg [.] test_thread+0x12 [.] test_thread+0x2c
2.16% test_prg test_prg [.] test_thread+0x2c [.] test_thread+0x14
0.02% test_prg [kernel.vmlinux] [k] asm_sysvec_apic_ti+0x5 [k] error_entry
Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kim Phillips <kim.phillips@amd.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Link: http://lore.kernel.org/lkml/20220208211637.2221872-13-eranian@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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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.