libperf: Add support for user space counter access

2021-04-20T11:10:45+00:00

x86 and arm64 can both support direct access of event counters in
userspace. The access sequence is less than trivial and currently exists
in perf test code (tools/perf/arch/x86/tests/rdpmc.c) with copies in
projects such as PAPI and libpfm4.

In order to support userspace access, an event must be mmapped first
with perf_evsel__mmap(). Then subsequent calls to perf_evsel__read()
will use the fast path (assuming the arch supports it).

Committer notes:

Added a '__maybe_unused' attribute to the read_perf_counter() argument
to fix the build on arches other than x86_64 and arm.

Committer testing:

  Building and running the libperf tests in verbose mode (V=1) now shows
  those "loop = N, count = N" extra lines, testing user space counter
  access.

  # make V=1 -C tools/lib/perf tests
  make: Entering directory '/home/acme/git/perf/tools/lib/perf'
  make -f /home/acme/git/perf/tools/build/Makefile.build dir=. obj=libperf
  make -C /home/acme/git/perf/tools/lib/api/ O= libapi.a
  make -f /home/acme/git/perf/tools/build/Makefile.build dir=./fd obj=libapi
  make -f /home/acme/git/perf/tools/build/Makefile.build dir=./fs obj=libapi
  make -C tests
  gcc -I/home/acme/git/perf/tools/lib/perf/include -I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -o test-cpumap-a test-cpumap.c ../libperf.a /home/acme/git/perf/tools/lib/api/libapi.a
  gcc -I/home/acme/git/perf/tools/lib/perf/include -I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -o test-threadmap-a test-threadmap.c ../libperf.a /home/acme/git/perf/tools/lib/api/libapi.a
  gcc -I/home/acme/git/perf/tools/lib/perf/include -I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -o test-evlist-a test-evlist.c ../libperf.a /home/acme/git/perf/tools/lib/api/libapi.a
  gcc -I/home/acme/git/perf/tools/lib/perf/include -I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -o test-evsel-a test-evsel.c ../libperf.a /home/acme/git/perf/tools/lib/api/libapi.a
  gcc -I/home/acme/git/perf/tools/lib/perf/include -I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -L.. -o test-cpumap-so test-cpumap.c /home/acme/git/perf/tools/lib/api/libapi.a -lperf
  gcc -I/home/acme/git/perf/tools/lib/perf/include -I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -L.. -o test-threadmap-so test-threadmap.c /home/acme/git/perf/tools/lib/api/libapi.a -lperf
  gcc -I/home/acme/git/perf/tools/lib/perf/include -I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -L.. -o test-evlist-so test-evlist.c /home/acme/git/perf/tools/lib/api/libapi.a -lperf
  gcc -I/home/acme/git/perf/tools/lib/perf/include -I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -L.. -o test-evsel-so test-evsel.c /home/acme/git/perf/tools/lib/api/libapi.a -lperf
  make -C tests run
  running static:
  - running test-cpumap.c...OK
  - running test-threadmap.c...OK
  - running test-evlist.c...OK
  - running test-evsel.c...
  	loop = 65536, count = 333926
  	loop = 131072, count = 655781
  	loop = 262144, count = 1311141
  	loop = 524288, count = 2630126
  	loop = 1048576, count = 5256955
  	loop = 65536, count = 524594
  	loop = 131072, count = 1058916
  	loop = 262144, count = 2097458
  	loop = 524288, count = 4205429
  	loop = 1048576, count = 8406606
  OK
  running dynamic:
  - running test-cpumap.c...OK
  - running test-threadmap.c...OK
  - running test-evlist.c...OK
  - running test-evsel.c...
  	loop = 65536, count = 328102
  	loop = 131072, count = 655782
  	loop = 262144, count = 1317494
  	loop = 524288, count = 2627851
  	loop = 1048576, count = 5255187
  	loop = 65536, count = 524601
  	loop = 131072, count = 1048923
  	loop = 262144, count = 2107917
  	loop = 524288, count = 4194606
  	loop = 1048576, count = 8409322
  OK
  make: Leaving directory '/home/acme/git/perf/tools/lib/perf'
  #

Signed-off-by: Rob Herring 
Acked-by: Jiri Olsa 
Acked-by: Namhyung Kim 
Tested-by: Arnaldo Carvalho de Melo 
Cc: Catalin Marinas 
Cc: Itaru Kitayama 
Cc: Mark Rutland 
Cc: Peter Zijlstra 
Cc: Will Deacon 
Link: http://lore.kernel.org/lkml/20210414155412.3697605-4-robh@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

libperf: Add evsel mmap support

2021-04-15T19:38:51+00:00

In order to support usersapce access, an event must be mmapped. While
there's already mmap support for evlist, the usecase is a bit different
than the self monitoring with userspace access. So let's add new
perf_evsel__mmap()/perf_evsel_munmap() functions to mmap/munmap an
evsel. This allows implementing userspace access as a fastpath for
perf_evsel__read().

The mmapped address is returned by perf_evsel__mmap_base() which
primarily for users/tests to check if userspace access is enabled.

Signed-off-by: Rob Herring 
Acked-by: Jiri Olsa 
Acked-by: Namhyung Kim 
Cc: Catalin Marinas 
Cc: Itaru Kitayama 
Cc: Mark Rutland 
Cc: Peter Zijlstra 
Cc: Will Deacon 
Link: http://lore.kernel.org/lkml/20210414155412.3697605-2-robh@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

libperf: Move to tools/lib/perf

2020-01-06T14:46:09+00:00

Move libperf from its current location under tools/perf to a separate
directory under tools/lib/.

Also change various paths (mainly includes) to reflect the libperf move
to a separate directory and add a new directory under MANIFEST.

Signed-off-by: Jiri Olsa 
Tested-by: Arnaldo Carvalho de Melo 
Cc: Alexander Shishkin 
Cc: Michael Petlan 
Cc: Namhyung Kim 
Cc: Peter Zijlstra 
Link: http://lore.kernel.org/lkml/20191206210612.8676-2-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

linux.git/tools/lib/perf/evsel.c, branch v5.13

libperf: Add support for user space counter access

libperf: Add evsel mmap support

libperf: Move to tools/lib/perf