Re: [PATCH -tip v3 0/6] perf: Introduce branch sub commands

[Akihiro Nagai]

(2011/04/01 23:43), Frederic Weisbecker wrote:
> On Thu, Mar 24, 2011 at 08:31:37PM +0900, Akihiro Nagai wrote:
> > Hi,
> >
> > This patch series provides the commands 'perf branch record' and 'perf branch trace'
> > version 3. These commands record and analyze a BTS (Branch Trace Store) log.
> > And, they provide the interface to use BTS log for application developers.
> >
> > BTS is a facility of Intel x86 processors, which records the address of
> > 'branch to/from' on every branch/jump instruction and interrupt.
> > This facility is very useful for developers to test their software,
> > for example, coverage test, execution path analysis, dynamic step count ...etc.
> > These test tools have a big advantage, which user doesn't have to modify target
> > executable binaries, because the BTS is a hardware feauture.
> >
> > But, there are few applications using BTS. Reasons I guess are ...
> >   - Few people know what BTS is.
> >   - Few people know how to use BTS on Linux box.
> >   - It's hard to analyze the BTS log because it includes just a series of addresses.
> >
> > So, I want to provide a user-friendly interface to BTS for application developers.
> >
> >
> >   About new sub commands
> > ========================
> > 'perf branch record' provides an easy way to record BTS log.
> > Usage is 'perf branch record<command>'.  This command is just an alias to
> > 'perf record -e branches:u -c 1<command>'. But, new one is more simple and
> > more intuitive.
> >
> > 'perf branch trace' can parse and analyze recorded BTS log and print various
> > information of execution path. This command can show address, pid, command name,
> > function+offset, file path of elf.
> > You can choose the printed information with option.
> >
> > Example: 'perf branch trace'
> > function+offset
> > irq_return+0x0  =>  _start+0x0
> > irq_return+0x0  =>  _start+0x0
> > _start+0x3      =>  _dl_start+0x0
> > irq_return+0x0  =>  _dl_start+0x0
> > irq_return+0x0  =>  _dl_start+0x26
> > irq_return+0x0  =>  _dl_start+0x2d
> > _dl_start+0x71  =>  _dl_start+0x93
> > _dl_start+0x97  =>  _dl_start+0x78
> > ...
> >
> > This is the default behavior of 'perf branch trace'. It prints function+offset.
> >
> >
> > Example2: 'perf branch -cas trace'
> > command address            function+offset
> > ls      0xffffffff8146fe0e irq_return+0x0  =>  ls   0x0000003806200b20 _start+0x0
>
> You probably want to display the comm (and/or the pid/tid) only once. Those are not
> going to change between the source and destination.
Exactly, perf_sample has only one pid/tid field.
So, pid/tid and command don't change between source and destination.
I'll remove desitination's pid/tid and command fields.
Thank you.
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