Em Sat, Jul 18, 2015 at 08:24:45AM -0700, Andi Kleen escreveu: > [v2: Addressed review comments. Fixed display problems and > correctly compute IPC now. See patches for detailed changes.] > [v3: Merged with current Arnaldo perf/core and added acked-by.] > > [Note the respective kernel patches to report cycles are in > peterz's perf/core queue, but so far not in tip. The patchkit > can be tested however with the "fake cycles" debug patch added at > the end] > > The upcoming Skylake CPU has a new timed branch stack feature, > that reports cycle counts for individual branches in the > last branch record. > > This allows to get fine grained cost information for code, and also allows > to compute fine grained IPC.
Thanks, applied.
- Arnaldo
> Available from
> git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc.git
> perf/skl-tools3
>
> This patchkit adds support for this in the perf tools:
> - Basic support for the cycles field like other branch fields
> - Show cycles in the standard branch sort view (no IPC here,
> as IPC needs the instruction counts from annotation)
> - Annotate cycles and IPC in the assembler annotate view
> - Add branch support to top, so we can do live annotation.
> - Misc support, like dumping it in perf report -D
>
> Example output for annotate (with made up numbers):
>
> The second column is the IPC and third average cycles for the basic block.
>
> │ static int hex(char ch)
> ▒
> │ {
> ▒
> 0.12 │ push %rbp
> ◆
> 0.12 │ mov %rsp,%rbp
> ▒
> 0.12 │ sub $0x20,%rsp
> ▒
> 0.12 │ mov %edi,%eax
> ▒
> 0.12 │ mov %al,-0x14(%rbp)
> ▒
> 0.12 │ mov %fs:0x28,%rax
> ▒
> 0.12 │ mov %rax,-0x8(%rbp)
> ▒
> 0.12 │ xor %eax,%eax
> ▒
> │ if ((ch >= '0') && (ch <= '9'))
> ▒
> 0.12 │ cmpb $0x2f,-0x14(%rbp)
> ▒
> 66.67 0.12 123 │ ↓ jle 31
> ▒
> 0.12 │ cmpb $0x39,-0x14(%rbp)
> ▒
> 0.12 123 │ ↓ jg 31
> ▒
> │ return ch - '0';
> ▒
> 22.22 0.12 │ movsbl -0x14(%rbp),%eax
> ▒
> 0.12 │ sub $0x30,%eax
> ▒
> 0.12 123 │ ↓ jmp 60
> ▒
> │ if ((ch >= 'a') && (ch <= 'f'))
> ▒
> 0.06 │31: cmpb $0x60,-0x14(%rbp)
> ▒
> 0.06 123 │ ↓ jle 46
> ▒
> 0.06 │ cmpb $0x66,-0x14(%rbp)
> ▒
> 0.06 │ ↓ jg 46
> ▒
> │ return ch - 'a' + 10;
> ▒
> 0.06 │ movsbl -0x14(%rbp),%eax
>
>
> Example output for branch view (again with fake data):
>
> Overhead Command Source Shared Object Source Symbol
> Target Symbol Basic Block Cycles ◆
> 30.08% tcall tcall [.] f1
> [.] f2 123 ▒
> 27.44% tcall tcall [.] f2
> [.] f1 123 ▒
> 15.60% tcall tcall [.] main
> [.] f1 123 ▒
> 12.96% tcall tcall [.] f1
> [.] main 123 ▒
> 12.86% tcall tcall [.] main
> [.] main 123 ▒
> 0.08% tcall [kernel.kallsyms] [k] hrtimer_interrupt
> [k] hrtimer_interrupt 123
>
> IPC computation has a few limitations (see the comments in the respective
> patches),
> in particular it punts on overlaping basic blocks.
>
> The annotation only works for the interactive annotation. Currently it is not
> working in the scripted perf annotate, as that is missing a lot of the
> infrastructure needed for per instruction state.
>
> It would be nice to add column headers to annotate.
>
> So far no support in --branch-history or in perf script.
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