<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/tools/lib, branch v4.16.13</title>
<subtitle>Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git</subtitle>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/'/>
<entry>
<title>objtool, perf: Fix GCC 8 -Wrestrict error</title>
<updated>2018-05-01T19:47:29+00:00</updated>
<author>
<name>Josh Poimboeuf</name>
<email>jpoimboe@redhat.com</email>
</author>
<published>2018-03-16T03:11:54+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=4b0110291ae1d618384cab105b1e2d208a31a6e3'/>
<id>4b0110291ae1d618384cab105b1e2d208a31a6e3</id>
<content type='text'>
commit 854e55ad289ef8888e7991f0ada85d5846f5afb9 upstream.

Starting with recent GCC 8 builds, objtool and perf fail to build with
the following error:

  ../str_error_r.c: In function ‘str_error_r’:
  ../str_error_r.c:25:3: error: passing argument 1 to restrict-qualified parameter aliases with argument 5 [-Werror=restrict]
     snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);

The code seems harmless, but there's probably no benefit in printing the
'buf' pointer in this situation anyway, so just remove it to make GCC
happy.

Reported-by: Laura Abbott &lt;labbott@redhat.com&gt;
Signed-off-by: Josh Poimboeuf &lt;jpoimboe@redhat.com&gt;
Tested-by: Laura Abbott &lt;labbott@redhat.com&gt;
Cc: Adrian Hunter &lt;adrian.hunter@intel.com&gt;
Cc: Jiri Olsa &lt;jolsa@kernel.org&gt;
Cc: Namhyung Kim &lt;namhyung@kernel.org&gt;
Cc: Wang Nan &lt;wangnan0@huawei.com&gt;
Link: http://lkml.kernel.org/r/20180316031154.juk2uncs7baffctp@treble
Signed-off-by: Arnaldo Carvalho de Melo &lt;acme@redhat.com&gt;
Cc: Fredrik Schön &lt;fredrikschon@gmail.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 854e55ad289ef8888e7991f0ada85d5846f5afb9 upstream.

Starting with recent GCC 8 builds, objtool and perf fail to build with
the following error:

  ../str_error_r.c: In function ‘str_error_r’:
  ../str_error_r.c:25:3: error: passing argument 1 to restrict-qualified parameter aliases with argument 5 [-Werror=restrict]
     snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);

The code seems harmless, but there's probably no benefit in printing the
'buf' pointer in this situation anyway, so just remove it to make GCC
happy.

Reported-by: Laura Abbott &lt;labbott@redhat.com&gt;
Signed-off-by: Josh Poimboeuf &lt;jpoimboe@redhat.com&gt;
Tested-by: Laura Abbott &lt;labbott@redhat.com&gt;
Cc: Adrian Hunter &lt;adrian.hunter@intel.com&gt;
Cc: Jiri Olsa &lt;jolsa@kernel.org&gt;
Cc: Namhyung Kim &lt;namhyung@kernel.org&gt;
Cc: Wang Nan &lt;wangnan0@huawei.com&gt;
Link: http://lkml.kernel.org/r/20180316031154.juk2uncs7baffctp@treble
Signed-off-by: Arnaldo Carvalho de Melo &lt;acme@redhat.com&gt;
Cc: Fredrik Schön &lt;fredrikschon@gmail.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>tools/libbpf: Avoid possibly using uninitialized variable</title>
<updated>2018-02-20T20:08:20+00:00</updated>
<author>
<name>Jeremy Cline</name>
<email>jeremy@jcline.org</email>
</author>
<published>2018-02-20T01:00:07+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=b1a2ce825737b0165cc08e6f98f8c0ea1affdd60'/>
<id>b1a2ce825737b0165cc08e6f98f8c0ea1affdd60</id>
<content type='text'>
Fixes a GCC maybe-uninitialized warning introduced by 48cca7e44f9f.
"text" is only initialized inside the if statement so only print debug
info there.

Fixes: 48cca7e44f9f ("libbpf: add support for bpf_call")
Signed-off-by: Jeremy Cline &lt;jeremy@jcline.org&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Fixes a GCC maybe-uninitialized warning introduced by 48cca7e44f9f.
"text" is only initialized inside the if statement so only print debug
info there.

Fixes: 48cca7e44f9f ("libbpf: add support for bpf_call")
Signed-off-by: Jeremy Cline &lt;jeremy@jcline.org&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf</title>
<updated>2018-02-09T19:05:10+00:00</updated>
<author>
<name>David S. Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2018-02-09T19:05:10+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=437a4db66df3bc9f139cfbfc66913ea207d9162a'/>
<id>437a4db66df3bc9f139cfbfc66913ea207d9162a</id>
<content type='text'>
Daniel Borkmann says:

====================
pull-request: bpf 2018-02-09

The following pull-request contains BPF updates for your *net* tree.

The main changes are:

1) Two fixes for BPF sockmap in order to break up circular map references
   from programs attached to sockmap, and detaching related sockets in
   case of socket close() event. For the latter we get rid of the
   smap_state_change() and plug into ULP infrastructure, which will later
   also be used for additional features anyway such as TX hooks. For the
   second issue, dependency chain is broken up via map release callback
   to free parse/verdict programs, all from John.

2) Fix a libbpf relocation issue that was found while implementing XDP
   support for Suricata project. Issue was that when clang was invoked
   with default target instead of bpf target, then various other e.g.
   debugging relevant sections are added to the ELF file that contained
   relocation entries pointing to non-BPF related sections which libbpf
   trips over instead of skipping them. Test cases for libbpf are added
   as well, from Jesper.

3) Various misc fixes for bpftool and one for libbpf: a small addition
   to libbpf to make sure it recognizes all standard section prefixes.
   Then, the Makefile in bpftool/Documentation is improved to explicitly
   check for rst2man being installed on the system as we otherwise risk
   installing empty man pages; the man page for bpftool-map is corrected
   and a set of missing bash completions added in order to avoid shipping
   bpftool where the completions are only partially working, from Quentin.

4) Fix applying the relocation to immediate load instructions in the
   nfp JIT which were missing a shift, from Jakub.

5) Two fixes for the BPF kernel selftests: handle CONFIG_BPF_JIT_ALWAYS_ON=y
   gracefully in test_bpf.ko module and mark them as FLAG_EXPECTED_FAIL
   in this case; and explicitly delete the veth devices in the two tests
   test_xdp_{meta,redirect}.sh before dismantling the netnses as when
   selftests are run in batch mode, then workqueue to handle destruction
   might not have finished yet and thus veth creation in next test under
   same dev name would fail, from Yonghong.

6) Fix test_kmod.sh to check the test_bpf.ko module path before performing
   an insmod, and fallback to modprobe. Especially the latter is useful
   when having a device under test that has the modules installed instead,
   from Naresh.
====================

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Daniel Borkmann says:

====================
pull-request: bpf 2018-02-09

The following pull-request contains BPF updates for your *net* tree.

The main changes are:

1) Two fixes for BPF sockmap in order to break up circular map references
   from programs attached to sockmap, and detaching related sockets in
   case of socket close() event. For the latter we get rid of the
   smap_state_change() and plug into ULP infrastructure, which will later
   also be used for additional features anyway such as TX hooks. For the
   second issue, dependency chain is broken up via map release callback
   to free parse/verdict programs, all from John.

2) Fix a libbpf relocation issue that was found while implementing XDP
   support for Suricata project. Issue was that when clang was invoked
   with default target instead of bpf target, then various other e.g.
   debugging relevant sections are added to the ELF file that contained
   relocation entries pointing to non-BPF related sections which libbpf
   trips over instead of skipping them. Test cases for libbpf are added
   as well, from Jesper.

3) Various misc fixes for bpftool and one for libbpf: a small addition
   to libbpf to make sure it recognizes all standard section prefixes.
   Then, the Makefile in bpftool/Documentation is improved to explicitly
   check for rst2man being installed on the system as we otherwise risk
   installing empty man pages; the man page for bpftool-map is corrected
   and a set of missing bash completions added in order to avoid shipping
   bpftool where the completions are only partially working, from Quentin.

4) Fix applying the relocation to immediate load instructions in the
   nfp JIT which were missing a shift, from Jakub.

5) Two fixes for the BPF kernel selftests: handle CONFIG_BPF_JIT_ALWAYS_ON=y
   gracefully in test_bpf.ko module and mark them as FLAG_EXPECTED_FAIL
   in this case; and explicitly delete the veth devices in the two tests
   test_xdp_{meta,redirect}.sh before dismantling the netnses as when
   selftests are run in batch mode, then workqueue to handle destruction
   might not have finished yet and thus veth creation in next test under
   same dev name would fail, from Yonghong.

6) Fix test_kmod.sh to check the test_bpf.ko module path before performing
   an insmod, and fallback to modprobe. Especially the latter is useful
   when having a device under test that has the modules installed instead,
   from Naresh.
====================

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>tools/libbpf: handle issues with bpf ELF objects containing .eh_frames</title>
<updated>2018-02-08T23:25:12+00:00</updated>
<author>
<name>Jesper Dangaard Brouer</name>
<email>brouer@redhat.com</email>
</author>
<published>2018-02-08T11:48:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=e3d91b0ca523d53158f435a3e13df7f0cb360ea2'/>
<id>e3d91b0ca523d53158f435a3e13df7f0cb360ea2</id>
<content type='text'>
V3: More generic skipping of relo-section (suggested by Daniel)

If clang &gt;= 4.0.1 is missing the option '-target bpf', it will cause
llc/llvm to create two ELF sections for "Exception Frames", with
section names '.eh_frame' and '.rel.eh_frame'.

The BPF ELF loader library libbpf fails when loading files with these
sections.  The other in-kernel BPF ELF loader in samples/bpf/bpf_load.c,
handle this gracefully. And iproute2 loader also seems to work with these
"eh" sections.

The issue in libbpf is caused by bpf_object__elf_collect() skipping
some sections, and later when performing relocation it will be
pointing to a skipped section, as these sections cannot be found by
bpf_object__find_prog_by_idx() in bpf_object__collect_reloc().

This is a general issue that also occurs for other sections, like
debug sections which are also skipped and can have relo section.

As suggested by Daniel.  To avoid keeping state about all skipped
sections, instead perform a direct qlookup in the ELF object.  Lookup
the section that the relo-section points to and check if it contains
executable machine instructions (denoted by the sh_flags
SHF_EXECINSTR).  Use this check to also skip irrelevant relo-sections.

Note, for samples/bpf/ the '-target bpf' parameter to clang cannot be used
due to incompatibility with asm embedded headers, that some of the samples
include. This is explained in more details by Yonghong Song in bpf_devel_QA.

Signed-off-by: Jesper Dangaard Brouer &lt;brouer@redhat.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
V3: More generic skipping of relo-section (suggested by Daniel)

If clang &gt;= 4.0.1 is missing the option '-target bpf', it will cause
llc/llvm to create two ELF sections for "Exception Frames", with
section names '.eh_frame' and '.rel.eh_frame'.

The BPF ELF loader library libbpf fails when loading files with these
sections.  The other in-kernel BPF ELF loader in samples/bpf/bpf_load.c,
handle this gracefully. And iproute2 loader also seems to work with these
"eh" sections.

The issue in libbpf is caused by bpf_object__elf_collect() skipping
some sections, and later when performing relocation it will be
pointing to a skipped section, as these sections cannot be found by
bpf_object__find_prog_by_idx() in bpf_object__collect_reloc().

This is a general issue that also occurs for other sections, like
debug sections which are also skipped and can have relo section.

As suggested by Daniel.  To avoid keeping state about all skipped
sections, instead perform a direct qlookup in the ELF object.  Lookup
the section that the relo-section points to and check if it contains
executable machine instructions (denoted by the sh_flags
SHF_EXECINSTR).  Use this check to also skip irrelevant relo-sections.

Note, for samples/bpf/ the '-target bpf' parameter to clang cannot be used
due to incompatibility with asm embedded headers, that some of the samples
include. This is explained in more details by Yonghong Song in bpf_devel_QA.

Signed-off-by: Jesper Dangaard Brouer &lt;brouer@redhat.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>tools/libbpf: improve the pr_debug statements to contain section numbers</title>
<updated>2018-02-08T23:24:38+00:00</updated>
<author>
<name>Jesper Dangaard Brouer</name>
<email>brouer@redhat.com</email>
</author>
<published>2018-02-08T11:48:17+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=077c066a6c5445423147496e6c9b9a2c2d2ee762'/>
<id>077c066a6c5445423147496e6c9b9a2c2d2ee762</id>
<content type='text'>
While debugging a bpf ELF loading issue, I needed to correlate the
ELF section number with the failed relocation section reference.
Thus, add section numbers/index to the pr_debug.

In debug mode, also print section that were skipped.  This helped
me identify that a section (.eh_frame) was skipped, and this was
the reason the relocation section (.rel.eh_frame) could not find
that section number.

The section numbers corresponds to the readelf tools Section Headers [Nr].

Signed-off-by: Jesper Dangaard Brouer &lt;brouer@redhat.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
While debugging a bpf ELF loading issue, I needed to correlate the
ELF section number with the failed relocation section reference.
Thus, add section numbers/index to the pr_debug.

In debug mode, also print section that were skipped.  This helped
me identify that a section (.eh_frame) was skipped, and this was
the reason the relocation section (.rel.eh_frame) could not find
that section number.

The section numbers corresponds to the readelf tools Section Headers [Nr].

Signed-off-by: Jesper Dangaard Brouer &lt;brouer@redhat.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>libbpf: complete list of strings for guessing program type</title>
<updated>2018-02-08T10:59:50+00:00</updated>
<author>
<name>Quentin Monnet</name>
<email>quentin.monnet@netronome.com</email>
</author>
<published>2018-02-08T04:27:13+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=0badd331491097cc3702d05a6dd0264a434712b2'/>
<id>0badd331491097cc3702d05a6dd0264a434712b2</id>
<content type='text'>
It seems that the type guessing feature for libbpf, based on the name of
the ELF section the program is located in, was inspired from
samples/bpf/prog_load.c, which was not used by any sample for loading
programs of certain types such as TC actions and classifiers, or
LWT-related types. As a consequence, libbpf is not able to guess the
type of such programs and to load them automatically if type is not
provided to the `bpf_load_prog()` function.

Add ELF section names associated to those eBPF program types so that
they can be loaded with e.g. bpftool as well.

Signed-off-by: Quentin Monnet &lt;quentin.monnet@netronome.com&gt;
Reviewed-by: Jakub Kicinski &lt;jakub.kicinski@netronome.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
It seems that the type guessing feature for libbpf, based on the name of
the ELF section the program is located in, was inspired from
samples/bpf/prog_load.c, which was not used by any sample for loading
programs of certain types such as TC actions and classifiers, or
LWT-related types. As a consequence, libbpf is not able to guess the
type of such programs and to load them automatically if type is not
provided to the `bpf_load_prog()` function.

Add ELF section names associated to those eBPF program types so that
they can be loaded with e.g. bpftool as well.

Signed-off-by: Quentin Monnet &lt;quentin.monnet@netronome.com&gt;
Reviewed-by: Jakub Kicinski &lt;jakub.kicinski@netronome.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'akpm' (patches from Andrew)</title>
<updated>2018-02-07T06:15:42+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2018-02-07T06:15:42+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=a2e5790d841658485d642196dbb0927303d6c22f'/>
<id>a2e5790d841658485d642196dbb0927303d6c22f</id>
<content type='text'>
Merge misc updates from Andrew Morton:

 - kasan updates

 - procfs

 - lib/bitmap updates

 - other lib/ updates

 - checkpatch tweaks

 - rapidio

 - ubsan

 - pipe fixes and cleanups

 - lots of other misc bits

* emailed patches from Andrew Morton &lt;akpm@linux-foundation.org&gt;: (114 commits)
  Documentation/sysctl/user.txt: fix typo
  MAINTAINERS: update ARM/QUALCOMM SUPPORT patterns
  MAINTAINERS: update various PALM patterns
  MAINTAINERS: update "ARM/OXNAS platform support" patterns
  MAINTAINERS: update Cortina/Gemini patterns
  MAINTAINERS: remove ARM/CLKDEV SUPPORT file pattern
  MAINTAINERS: remove ANDROID ION pattern
  mm: docs: add blank lines to silence sphinx "Unexpected indentation" errors
  mm: docs: fix parameter names mismatch
  mm: docs: fixup punctuation
  pipe: read buffer limits atomically
  pipe: simplify round_pipe_size()
  pipe: reject F_SETPIPE_SZ with size over UINT_MAX
  pipe: fix off-by-one error when checking buffer limits
  pipe: actually allow root to exceed the pipe buffer limits
  pipe, sysctl: remove pipe_proc_fn()
  pipe, sysctl: drop 'min' parameter from pipe-max-size converter
  kasan: rework Kconfig settings
  crash_dump: is_kdump_kernel can be boolean
  kernel/mutex: mutex_is_locked can be boolean
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Merge misc updates from Andrew Morton:

 - kasan updates

 - procfs

 - lib/bitmap updates

 - other lib/ updates

 - checkpatch tweaks

 - rapidio

 - ubsan

 - pipe fixes and cleanups

 - lots of other misc bits

* emailed patches from Andrew Morton &lt;akpm@linux-foundation.org&gt;: (114 commits)
  Documentation/sysctl/user.txt: fix typo
  MAINTAINERS: update ARM/QUALCOMM SUPPORT patterns
  MAINTAINERS: update various PALM patterns
  MAINTAINERS: update "ARM/OXNAS platform support" patterns
  MAINTAINERS: update Cortina/Gemini patterns
  MAINTAINERS: remove ARM/CLKDEV SUPPORT file pattern
  MAINTAINERS: remove ANDROID ION pattern
  mm: docs: add blank lines to silence sphinx "Unexpected indentation" errors
  mm: docs: fix parameter names mismatch
  mm: docs: fixup punctuation
  pipe: read buffer limits atomically
  pipe: simplify round_pipe_size()
  pipe: reject F_SETPIPE_SZ with size over UINT_MAX
  pipe: fix off-by-one error when checking buffer limits
  pipe: actually allow root to exceed the pipe buffer limits
  pipe, sysctl: remove pipe_proc_fn()
  pipe, sysctl: drop 'min' parameter from pipe-max-size converter
  kasan: rework Kconfig settings
  crash_dump: is_kdump_kernel can be boolean
  kernel/mutex: mutex_is_locked can be boolean
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>lib: optimize cpumask_next_and()</title>
<updated>2018-02-07T02:32:44+00:00</updated>
<author>
<name>Clement Courbet</name>
<email>courbet@google.com</email>
</author>
<published>2018-02-06T23:38:34+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=0ade34c37012ea5c516d9aa4d19a56e9f40a55ed'/>
<id>0ade34c37012ea5c516d9aa4d19a56e9f40a55ed</id>
<content type='text'>
We've measured that we spend ~0.6% of sys cpu time in cpumask_next_and().
It's essentially a joined iteration in search for a non-zero bit, which is
currently implemented as a lookup join (find a nonzero bit on the lhs,
lookup the rhs to see if it's set there).

Implement a direct join (find a nonzero bit on the incrementally built
join).  Also add generic bitmap benchmarks in the new `test_find_bit`
module for new function (see `find_next_and_bit` in [2] and [3] below).

For cpumask_next_and, direct benchmarking shows that it's 1.17x to 14x
faster with a geometric mean of 2.1 on 32 CPUs [1].  No impact on memory
usage.  Note that on Arm, the new pure-C implementation still outperforms
the old one that uses a mix of C and asm (`find_next_bit`) [3].

[1] Approximate benchmark code:

```
  unsigned long src1p[nr_cpumask_longs] = {pattern1};
  unsigned long src2p[nr_cpumask_longs] = {pattern2};
  for (/*a bunch of repetitions*/) {
    for (int n = -1; n &lt;= nr_cpu_ids; ++n) {
      asm volatile("" : "+rm"(src1p)); // prevent any optimization
      asm volatile("" : "+rm"(src2p));
      unsigned long result = cpumask_next_and(n, src1p, src2p);
      asm volatile("" : "+rm"(result));
    }
  }
```

Results:
pattern1    pattern2     time_before/time_after
0x0000ffff  0x0000ffff   1.65
0x0000ffff  0x00005555   2.24
0x0000ffff  0x00001111   2.94
0x0000ffff  0x00000000   14.0
0x00005555  0x0000ffff   1.67
0x00005555  0x00005555   1.71
0x00005555  0x00001111   1.90
0x00005555  0x00000000   6.58
0x00001111  0x0000ffff   1.46
0x00001111  0x00005555   1.49
0x00001111  0x00001111   1.45
0x00001111  0x00000000   3.10
0x00000000  0x0000ffff   1.18
0x00000000  0x00005555   1.18
0x00000000  0x00001111   1.17
0x00000000  0x00000000   1.25
-----------------------------
               geo.mean  2.06

[2] test_find_next_bit, X86 (skylake)

 [ 3913.477422] Start testing find_bit() with random-filled bitmap
 [ 3913.477847] find_next_bit: 160868 cycles, 16484 iterations
 [ 3913.477933] find_next_zero_bit: 169542 cycles, 16285 iterations
 [ 3913.478036] find_last_bit: 201638 cycles, 16483 iterations
 [ 3913.480214] find_first_bit: 4353244 cycles, 16484 iterations
 [ 3913.480216] Start testing find_next_and_bit() with random-filled
 bitmap
 [ 3913.481074] find_next_and_bit: 89604 cycles, 8216 iterations
 [ 3913.481075] Start testing find_bit() with sparse bitmap
 [ 3913.481078] find_next_bit: 2536 cycles, 66 iterations
 [ 3913.481252] find_next_zero_bit: 344404 cycles, 32703 iterations
 [ 3913.481255] find_last_bit: 2006 cycles, 66 iterations
 [ 3913.481265] find_first_bit: 17488 cycles, 66 iterations
 [ 3913.481266] Start testing find_next_and_bit() with sparse bitmap
 [ 3913.481272] find_next_and_bit: 764 cycles, 1 iterations

[3] test_find_next_bit, arm (v7 odroid XU3).

[  267.206928] Start testing find_bit() with random-filled bitmap
[  267.214752] find_next_bit: 4474 cycles, 16419 iterations
[  267.221850] find_next_zero_bit: 5976 cycles, 16350 iterations
[  267.229294] find_last_bit: 4209 cycles, 16419 iterations
[  267.279131] find_first_bit: 1032991 cycles, 16420 iterations
[  267.286265] Start testing find_next_and_bit() with random-filled
bitmap
[  267.302386] find_next_and_bit: 2290 cycles, 8140 iterations
[  267.309422] Start testing find_bit() with sparse bitmap
[  267.316054] find_next_bit: 191 cycles, 66 iterations
[  267.322726] find_next_zero_bit: 8758 cycles, 32703 iterations
[  267.329803] find_last_bit: 84 cycles, 66 iterations
[  267.336169] find_first_bit: 4118 cycles, 66 iterations
[  267.342627] Start testing find_next_and_bit() with sparse bitmap
[  267.356919] find_next_and_bit: 91 cycles, 1 iterations

[courbet@google.com: v6]
  Link: http://lkml.kernel.org/r/20171129095715.23430-1-courbet@google.com
[geert@linux-m68k.org: m68k/bitops: always include &lt;asm-generic/bitops/find.h&gt;]
  Link: http://lkml.kernel.org/r/1512556816-28627-1-git-send-email-geert@linux-m68k.org
Link: http://lkml.kernel.org/r/20171128131334.23491-1-courbet@google.com
Signed-off-by: Clement Courbet &lt;courbet@google.com&gt;
Signed-off-by: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Cc: Yury Norov &lt;ynorov@caviumnetworks.com&gt;
Cc: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Cc: Alexey Dobriyan &lt;adobriyan@gmail.com&gt;
Cc: Rasmus Villemoes &lt;linux@rasmusvillemoes.dk&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;

Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
We've measured that we spend ~0.6% of sys cpu time in cpumask_next_and().
It's essentially a joined iteration in search for a non-zero bit, which is
currently implemented as a lookup join (find a nonzero bit on the lhs,
lookup the rhs to see if it's set there).

Implement a direct join (find a nonzero bit on the incrementally built
join).  Also add generic bitmap benchmarks in the new `test_find_bit`
module for new function (see `find_next_and_bit` in [2] and [3] below).

For cpumask_next_and, direct benchmarking shows that it's 1.17x to 14x
faster with a geometric mean of 2.1 on 32 CPUs [1].  No impact on memory
usage.  Note that on Arm, the new pure-C implementation still outperforms
the old one that uses a mix of C and asm (`find_next_bit`) [3].

[1] Approximate benchmark code:

```
  unsigned long src1p[nr_cpumask_longs] = {pattern1};
  unsigned long src2p[nr_cpumask_longs] = {pattern2};
  for (/*a bunch of repetitions*/) {
    for (int n = -1; n &lt;= nr_cpu_ids; ++n) {
      asm volatile("" : "+rm"(src1p)); // prevent any optimization
      asm volatile("" : "+rm"(src2p));
      unsigned long result = cpumask_next_and(n, src1p, src2p);
      asm volatile("" : "+rm"(result));
    }
  }
```

Results:
pattern1    pattern2     time_before/time_after
0x0000ffff  0x0000ffff   1.65
0x0000ffff  0x00005555   2.24
0x0000ffff  0x00001111   2.94
0x0000ffff  0x00000000   14.0
0x00005555  0x0000ffff   1.67
0x00005555  0x00005555   1.71
0x00005555  0x00001111   1.90
0x00005555  0x00000000   6.58
0x00001111  0x0000ffff   1.46
0x00001111  0x00005555   1.49
0x00001111  0x00001111   1.45
0x00001111  0x00000000   3.10
0x00000000  0x0000ffff   1.18
0x00000000  0x00005555   1.18
0x00000000  0x00001111   1.17
0x00000000  0x00000000   1.25
-----------------------------
               geo.mean  2.06

[2] test_find_next_bit, X86 (skylake)

 [ 3913.477422] Start testing find_bit() with random-filled bitmap
 [ 3913.477847] find_next_bit: 160868 cycles, 16484 iterations
 [ 3913.477933] find_next_zero_bit: 169542 cycles, 16285 iterations
 [ 3913.478036] find_last_bit: 201638 cycles, 16483 iterations
 [ 3913.480214] find_first_bit: 4353244 cycles, 16484 iterations
 [ 3913.480216] Start testing find_next_and_bit() with random-filled
 bitmap
 [ 3913.481074] find_next_and_bit: 89604 cycles, 8216 iterations
 [ 3913.481075] Start testing find_bit() with sparse bitmap
 [ 3913.481078] find_next_bit: 2536 cycles, 66 iterations
 [ 3913.481252] find_next_zero_bit: 344404 cycles, 32703 iterations
 [ 3913.481255] find_last_bit: 2006 cycles, 66 iterations
 [ 3913.481265] find_first_bit: 17488 cycles, 66 iterations
 [ 3913.481266] Start testing find_next_and_bit() with sparse bitmap
 [ 3913.481272] find_next_and_bit: 764 cycles, 1 iterations

[3] test_find_next_bit, arm (v7 odroid XU3).

[  267.206928] Start testing find_bit() with random-filled bitmap
[  267.214752] find_next_bit: 4474 cycles, 16419 iterations
[  267.221850] find_next_zero_bit: 5976 cycles, 16350 iterations
[  267.229294] find_last_bit: 4209 cycles, 16419 iterations
[  267.279131] find_first_bit: 1032991 cycles, 16420 iterations
[  267.286265] Start testing find_next_and_bit() with random-filled
bitmap
[  267.302386] find_next_and_bit: 2290 cycles, 8140 iterations
[  267.309422] Start testing find_bit() with sparse bitmap
[  267.316054] find_next_bit: 191 cycles, 66 iterations
[  267.322726] find_next_zero_bit: 8758 cycles, 32703 iterations
[  267.329803] find_last_bit: 84 cycles, 66 iterations
[  267.336169] find_first_bit: 4118 cycles, 66 iterations
[  267.342627] Start testing find_next_and_bit() with sparse bitmap
[  267.356919] find_next_and_bit: 91 cycles, 1 iterations

[courbet@google.com: v6]
  Link: http://lkml.kernel.org/r/20171129095715.23430-1-courbet@google.com
[geert@linux-m68k.org: m68k/bitops: always include &lt;asm-generic/bitops/find.h&gt;]
  Link: http://lkml.kernel.org/r/1512556816-28627-1-git-send-email-geert@linux-m68k.org
Link: http://lkml.kernel.org/r/20171128131334.23491-1-courbet@google.com
Signed-off-by: Clement Courbet &lt;courbet@google.com&gt;
Signed-off-by: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Cc: Yury Norov &lt;ynorov@caviumnetworks.com&gt;
Cc: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Cc: Alexey Dobriyan &lt;adobriyan@gmail.com&gt;
Cc: Rasmus Villemoes &lt;linux@rasmusvillemoes.dk&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;

Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>tools/lib/subcmd/pager.c: do not alias select() params</title>
<updated>2018-02-07T02:32:44+00:00</updated>
<author>
<name>Sergey Senozhatsky</name>
<email>sergey.senozhatsky@gmail.com</email>
</author>
<published>2018-02-06T23:37:52+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=ad343a98e74e85aa91d844310e797f96fee6983b'/>
<id>ad343a98e74e85aa91d844310e797f96fee6983b</id>
<content type='text'>
Use a separate fd set for select()-s exception fds param to fix the
following gcc warning:

  pager.c:36:12: error: passing argument 2 to restrict-qualified parameter aliases with argument 4 [-Werror=restrict]
    select(1, &amp;in, NULL, &amp;in, NULL);
              ^~~        ~~~

Link: http://lkml.kernel.org/r/20180101105626.7168-1-sergey.senozhatsky@gmail.com
Signed-off-by: Sergey Senozhatsky &lt;sergey.senozhatsky@gmail.com&gt;
Cc: Arnaldo Carvalho de Melo &lt;acme@redhat.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Use a separate fd set for select()-s exception fds param to fix the
following gcc warning:

  pager.c:36:12: error: passing argument 2 to restrict-qualified parameter aliases with argument 4 [-Werror=restrict]
    select(1, &amp;in, NULL, &amp;in, NULL);
              ^~~        ~~~

Link: http://lkml.kernel.org/r/20180101105626.7168-1-sergey.senozhatsky@gmail.com
Signed-off-by: Sergey Senozhatsky &lt;sergey.senozhatsky@gmail.com&gt;
Cc: Arnaldo Carvalho de Melo &lt;acme@redhat.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>libbpf: add missing SPDX-License-Identifier</title>
<updated>2018-02-03T01:53:48+00:00</updated>
<author>
<name>Eric Leblond</name>
<email>eric@regit.org</email>
</author>
<published>2018-01-30T20:55:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=6061a3d6720600c976b877c3ac1402b3ef0a8a55'/>
<id>6061a3d6720600c976b877c3ac1402b3ef0a8a55</id>
<content type='text'>
Signed-off-by: Eric Leblond &lt;eric@regit.org&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Signed-off-by: Eric Leblond &lt;eric@regit.org&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
</pre>
</div>
</content>
</entry>
</feed>
