be316409e9
This is already present in 'perf top', albeit undocumented (will fix),
and is useful to use /proc/kcore instead of vmlinux and then get what is
really in place, not what the kernel starts with, before alternatives,
ftrace .text patching, etc, see the differences:
# perf annotate --stdio2 _raw_spin_lock_irqsave
_raw_spin_lock_irqsave() /lib/modules/4.16.0-rc4/build/vmlinux
Event: anon group { cycles, instructions }
0.00 3.17 → callq __fentry__
0.00 7.94 push %rbx
7.69 36.51 → callq __page_file_index
mov %rax,%rbx
7.69 3.17 → callq *ffffffff82225cd0
xor %eax,%eax
mov $0x1,%edx
80.77 49.21 lock cmpxchg %edx,(%rdi)
test %eax,%eax
↓ jne 2b
3.85 0.00 mov %rbx,%rax
pop %rbx
← retq
2b: mov %eax,%esi
→ callq queued_spin_lock_slowpath
mov %rbx,%rax
pop %rbx
← retq
[root@jouet ~]# perf annotate --ignore-vmlinux --stdio2 _raw_spin_lock_irqsave
_raw_spin_lock_irqsave() /proc/kcore
Event: anon group { cycles, instructions }
0.00 3.17 nop
0.00 7.94 push %rbx
0.00 23.81 pushfq
7.69 12.70 pop %rax
nop
mov %rax,%rbx
7.69 3.17 cli
nop
xor %eax,%eax
mov $0x1,%edx
80.77 49.21 lock cmpxchg %edx,(%rdi)
test %eax,%eax
↓ jne 2b
3.85 0.00 mov %rbx,%rax
pop %rbx
← retq
2b: mov %eax,%esi
→ callq *ffffffff820e96b0
mov %rbx,%rax
pop %rbx
← retq
#
Diff of the output of those commands:
# perf annotate --stdio2 _raw_spin_lock_irqsave > /tmp/vmlinux
# perf annotate --ignore-vmlinux --stdio2 _raw_spin_lock_irqsave > /tmp/kcore
# diff -y /tmp/vmlinux /tmp/kcore
_raw_spin_lock_irqsave() vmlinux | _raw_spin_lock_irqsave() /proc/kcore
Event: anon group { cycles, instructions } Event: anon group { cycles, instructions }
0.00 3.17 → callq __fentry__ | 0.00 3.17 nop
0.00 7.94 push %rbx 0.00 7.94 push %rbx
7.69 36.51 → callq __page_file_index | 0.00 23.81 pushfq
> 7.69 12.70 pop %rax
> nop
mov %rax,%rbx mov %rax,%rbx
7.69 3.17 → callq *ffffffff82225cd0 | 7.69 3.17 cli
> nop
xor %eax,%eax xor %eax,%eax
mov $0x1,%edx mov $0x1,%edx
80.77 49.21 lock cmpxchg %edx,(%rdi) 80.77 49.21 lock cmpxchg %edx,(%rdi)
test %eax,%eax test %eax,%eax
↓ jne 2b ↓ jne 2b
3.85 0.00 mov %rbx,%rax 3.85 0.00 mov %rbx,%rax
pop %rbx pop %rbx
← retq ← retq
2b: mov %eax,%esi 2b: mov %eax,%esi
→ callq queued_spin_lock_slowpath| → callq *ffffffff820e96b0
mov %rbx,%rax mov %rbx,%rax
pop %rbx pop %rbx
← retq ← retq
#
This should be further streamlined by doing both annotations and
allowing the TUI to toggle initial/current, and show the patched
instructions in a slightly different color.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-wz8d269hxkcwaczr0r4rhyjg@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.