adc218676e
5 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Andi Kleen
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bf0db8c759 |
perf script: Minimize "not reaching sample" for '-F +brstackinsn'
In some situations 'perf script -F +brstackinsn' sees a lot of "not
reaching sample" messages.
This happens when the last LBR block before the sample contains a branch
that is not in the LBR, and the instruction dumping stops.
$ perf record -b emacs -Q --batch '()'
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.396 MB perf.data (443 samples) ]
$ perf script -F +brstackinsn
...
00007f0ab2d171a4 insn: 41 0f 94 c0
00007f0ab2d171a8 insn: 83 fa 01
00007f0ab2d171ab insn: 74 d3 # PRED 6 cycles [313] 1.00 IPC
00007f0ab2d17180 insn: 45 84 c0
00007f0ab2d17183 insn: 74 28
... not reaching sample ...
$ perf script -F +brstackinsn | grep -c reach
136
$
This is a problem for further analysis that wants to see the full code
upto the sample.
There are two common cases where the message is bogus:
- The LBR only logs taken branches, but the branch might be a
conditional branch that is not taken (that is the most common case
actually)
- The LBR sampling uses a filter ignoring some branches, but the perf
script check checks for all branches.
This patch fixes these two conditions, by only checking for conditional
branches, as well as checking the perf_event_attr's branch filter
attributes.
For the test case above it fixes all the messages:
$ ./perf script -F +brstackinsn | grep -c reach
0
Note that there are still conditions when the message is hit --
sometimes there can be a unconditional branch that misses the LBR update
before the sample -- but they are much more rare now.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20240229161828.386397-1-ak@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Andi Kleen
|
d812044688 |
perf script: Add capstone support for '-F +brstackdisasm'
Support capstone output for the '-F +brstackinsn' branch dump.
The new output is enabled with the new field 'brstackdisasm'.
This was possible before with --xed, but now also allow it for users
that don't have xed using the builtin capstone support.
Before:
perf record -b emacs -Q --batch '()'
perf script -F +brstackinsn
...
emacs 55778 1814366.755945: 151564 cycles:P: 7f0ab2d17192 intel_check_word.constprop.0+0x162 (/usr/lib64/ld-linux-x86-64.s> intel_check_word.constprop.0+237:
00007f0ab2d1711d insn: 75 e6 # PRED 3 cycles [3]
00007f0ab2d17105 insn: 73 51
00007f0ab2d17107 insn: 48 89 c1
00007f0ab2d1710a insn: 48 39 ca
00007f0ab2d1710d insn: 73 96
00007f0ab2d1710f insn: 48 8d 04 11
00007f0ab2d17113 insn: 48 d1 e8
00007f0ab2d17116 insn: 49 8d 34 c1
00007f0ab2d1711a insn: 44 3a 06
00007f0ab2d1711d insn: 75 e6 # PRED 3 cycles [6] 3.00 IPC
00007f0ab2d17105 insn: 73 51 # PRED 1 cycles [7] 1.00 IPC
00007f0ab2d17158 insn: 48 8d 50 01
00007f0ab2d1715c insn: eb 92 # PRED 1 cycles [8] 2.00 IPC
00007f0ab2d170f0 insn: 48 39 ca
00007f0ab2d170f3 insn: 73 b0 # PRED 1 cycles [9] 2.00 IPC
After (perf must be compiled with capstone):
perf script -F +brstackdisasm
...
emacs 55778 1814366.755945: 151564 cycles:P: 7f0ab2d17192 intel_check_word.constprop.0+0x162 (/usr/lib64/ld-linux-x86-64.s> intel_check_word.constprop.0+237:
00007f0ab2d1711d jne intel_check_word.constprop.0+0xd5 # PRED 3 cycles [3]
00007f0ab2d17105 jae intel_check_word.constprop.0+0x128
00007f0ab2d17107 movq %rax, %rcx
00007f0ab2d1710a cmpq %rcx, %rdx
00007f0ab2d1710d jae intel_check_word.constprop.0+0x75
00007f0ab2d1710f leaq (%rcx, %rdx), %rax
00007f0ab2d17113 shrq $1, %rax
00007f0ab2d17116 leaq (%r9, %rax, 8), %rsi
00007f0ab2d1711a cmpb (%rsi), %r8b
00007f0ab2d1711d jne intel_check_word.constprop.0+0xd5 # PRED 3 cycles [6] 3.00 IPC
00007f0ab2d17105 jae intel_check_word.constprop.0+0x128 # PRED 1 cycles [7] 1.00 IPC
00007f0ab2d17158 leaq 1(%rax), %rdx
00007f0ab2d1715c jmp intel_check_word.constprop.0+0xc0 # PRED 1 cycles [8] 2.00 IPC
00007f0ab2d170f0 cmpq %rcx, %rdx
00007f0ab2d170f3 jae intel_check_word.constprop.0+0x75 # PRED 1 cycles [9] 2.00 IPC
Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: https://lore.kernel.org/r/20240401210925.209671-3-ak@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Andi Kleen
|
61f611593f |
perf script: Fix LBR skid dump problems in brstackinsn
This is a fix for another instance of the skid problem Milian recently
found [1]
The LBRs don't freeze at the exact same time as the PMI is triggered.
The perf script brstackinsn code that dumps LBR assembler assumes that
the last branch in the LBR leads to the sample point. But with skid
it's possible that the CPU executes one or more branches before the
sample, but which do not appear in the LBR.
What happens then is either that the sample point is before the last LBR
branch. In this case the dumper sees a negative length and ignores it.
Or it the sample point is long after the last branch. Then the dumper
sees a very long block and dumps it upto its block limit (16k bytes),
which is noise in the output.
On typical sample session this can happen regularly.
This patch tries to detect and handle the situation. On the last block
that is dumped by the LBR dumper we always stop on the first branch. If
the block length is negative just scan forward to the first branch.
Otherwise scan until a branch is found.
The PT decoder already has a function that uses the instruction decoder
to detect branches, so we can just reuse it here.
Then when a terminating branch is found print an indication and stop
dumping. This might miss a few instructions, but at least shows no
runaway blocks.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Link: http://lkml.kernel.org/r/20181120050617.4119-1-andi@firstfloor.org
[ Resolved conflict with
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Greg Kroah-Hartman
|
b24413180f |
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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Andi Kleen
|
48d02a1d5c |
perf script: Add 'brstackinsn' for branch stacks
Implement printing instruction sequences as hex dump for branch stacks.
This relies on the x86 instruction decoder used by the PT decoder to
find the lengths of instructions to dump them individually.
This is good enough for pattern matching.
This allows to study hot paths for individual samples, together with
branch misprediction and cycle count / IPC information if available (on
Skylake systems).
% perf record -b ...
% perf script -F brstackinsn
...
read_hpet+67:
ffffffff9905b843 insn: 74 ea # PRED
ffffffff9905b82f insn: 85 c9
ffffffff9905b831 insn: 74 12
ffffffff9905b833 insn: f3 90
ffffffff9905b835 insn: 48 8b 0f
ffffffff9905b838 insn: 48 89 ca
ffffffff9905b83b insn: 48 c1 ea 20
ffffffff9905b83f insn: 39 f2
ffffffff9905b841 insn: 89 d0
ffffffff9905b843 insn: 74 ea # PRED
Only works when no special branch filters are specified.
Occasionally the path does not reach up to the sample IP, as the LBRs
may be frozen before executing a final jump. In this case we print a
special message.
The instruction dumper piggy backs on the existing infrastructure from
the IP PT decoder.
An earlier iteration of this patch relied on a disassembler, but this
version only uses the existing instruction decoder.
Committer note:
Added hint about how to get suitable perf.data files for use with
'-F brstackinsm':
$ perf record usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.018 MB perf.data (8 samples) ]
$
$ perf script -F brstackinsn
Display of branch stack assembler requested, but non all-branch filter set
Hint: run 'perf record -b ...'
$
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Link: http://lkml.kernel.org/r/20170223234634.583-1-andi@firstfloor.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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