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SubjectRe: [PATCH -tip v4 0/5] perf script: add BTS analysis features
(2012/01/18 20:48), Frederic Weisbecker wrote:
> On Mon, Jan 16, 2012 at 02:21:46PM +0900, Akihiro Nagai wrote:
>> Hi Frederic, David,
>>
>> This patch series adds the functions to analyze BTS logs to perf-script and,
>> makes perf-script more informative version 4.
>> The patches add the following functions.
>> - Unify the expression to "[unknown]"
>> - Fix BTS record header to resolve DSOs and symbols of user-space
>> - Resolve DSOs and symbols for BTS's branch_from addresses
>> - Show the offset of symbols with the 'offs' field specifier.
>> - Resolve the real path of [kernel.kallsym] using
>> '--show-kernel-path' option.
>>
>> Usage:
>> First, get the BTS log with the following command.
>> # perf record -e branches:u -c 1 -d<command>
>>
>> Second, analyze that trace data.
>> # perf script -f ip,addr,sym,offs,dso [--show-kernel-path]
>> This command's output format is:
>> <branch_to addr> <branch_to function+offset> <branch_to DSO> <branch_from addr> <branch_from function+offset> <branch_from DSO>
>>
>> Output sample:
>> # perf record -e branches:u -c 1 -d ls
>> [snip]
>> # perf script -f ip,addr,sym,dso,offs --show-kernel-path
>> [snip]
>> 402c1c main+0x0 (/root/bin/ls) 3430c21399 __libc_start_main+0xe9 (/lib64/libc-2.14.so)
>
> I was confused first, looking for the reason why we have a so strange branch flow
> until I realized the format is "to from".
>
> Can we have "from to" instead? This will be much more intuitive. "from => to" would be even better.
Exactly.
perf records branch_to information in perf_sample->addr, and branch_from in perf_sample->ip.
And, currently I use the generic function: process_event() in builtin-script.c to print
branch information. This function prints perf_sample->addr before it prints perf_sample->ip.

So, I'm going to add the bts specialized codes to process_event().

static void process_event(...)
{
<snip>
print_sample_start(sample, thread, attr);
if (is_bts_event(attr)) {
print_sample_bts(...);
return;
}
if (PRINT_FIELD(TRACE))
<snip>
}
Thank you.
>
> Thanks!
>
>> 40b390 set_program_name+0x0 (/root/bin/ls) 402c41 main+0x25 (/root/bin/ls)
>> 40b390 set_program_name+0x0 (/root/bin/ls) ffffffff814ac5ed irq_return+0x0 (/lib/modules/3.2.0+/build/vmlinux)
>> 401e20 strrchr@plt+0x0 (/root/bin/ls) 40b39e set_program_name+0xe (/root/bin/ls)
>> 401e26 strrchr@plt+0x6 (/root/bin/ls) 401e20 strrchr@plt+0x0 (/root/bin/ls)
>> 401b80 _init+0x18 (/root/bin/ls) 401e2b strrchr@plt+0xb (/root/bin/ls)
>> 3430813850 _dl_runtime_resolve+0x0 (/lib64/ld-2.14.so) 401b86 _init+0x1e (/root/bin/ls)
>> [snip]
>


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