A hotspot patch for stack profiling (frame pointer)
Erik Helin
erik.helin at oracle.com
Tue Dec 9 09:53:00 UTC 2014
I applied the patch on top of jdk9/hs-comp and created a webrev:
http://cr.openjdk.java.net/~ehelin/brendan/frame-pointer/webrev/
I also successfully run the patch through JPRT.
Thanks,
Erik
On 2014-12-05 20:57, Brendan Gregg wrote:
>
>
> On Thu, Dec 4, 2014 at 2:55 PM, Brendan Gregg <brendan.d.gregg at gmail.com
> <mailto:brendan.d.gregg at gmail.com>> wrote:
>
> G'Day,
>
> I've hacked hotspot to return the frame pointer, in part to see what
> this involves, and also to have a working prototype for analysis.
> Along with an agent to resolve symbols, this has allowed full stack
> profiling using Linux perf_events. The following flame graphs show
> the resulting profiles.
>
> A mixed mode CPU flame graph of a vert.x benchmark (click to zoom):
>
> http://www.brendangregg.com/FlameGraphs/cpu-mixedmode-vertx.svg
>
> Same thing, but this time disabling inlining, to show more frames:
>
> http://www.brendangregg.com/FlameGraphs/cpu-mixedmode-flamegraph.svg
>
> As expected, performance is worse without inlining. You can compare
> the flame graphs side by side to see why. Less time spent doing work
> / I/O!
>
> https://github.com/brendangregg/Misc/blob/master/java/openjdk8_b132-fp.diff
> is my patch,
>
> [...]
>
>
> In case there's problems with the patch URL, the patch is:
>
> --- openjdk8clean/hotspot/src/cpu/x86/vm/x86_64.ad <http://x86_64.ad>
> 2014-03-04 02:52:11.000000000 +0000
> +++ openjdk8/hotspot/src/cpu/x86/vm/x86_64.ad <http://x86_64.ad>
> 2014-11-08 01:10:49.686044933 +0000
> @@ -166,10 +166,9 @@
> // 3) reg_class stack_slots( /* one chunk of stack-based "registers" */ )
> //
>
> -// Class for all pointer registers (including RSP)
> +// Class for all pointer registers (including RSP, excluding RBP)
> reg_class any_reg(RAX, RAX_H,
> RDX, RDX_H,
> - RBP, RBP_H,
> RDI, RDI_H,
> RSI, RSI_H,
> RCX, RCX_H,
> @@ -184,10 +183,9 @@
> R14, R14_H,
> R15, R15_H);
>
> -// Class for all pointer registers except RSP
> +// Class for all pointer registers except RSP and RBP
> reg_class ptr_reg(RAX, RAX_H,
> RDX, RDX_H,
> - RBP, RBP_H,
> RDI, RDI_H,
> RSI, RSI_H,
> RCX, RCX_H,
> @@ -199,9 +197,8 @@
> R13, R13_H,
> R14, R14_H);
>
> -// Class for all pointer registers except RAX and RSP
> +// Class for all pointer registers except RAX, RSP and RBP
> reg_class ptr_no_rax_reg(RDX, RDX_H,
> - RBP, RBP_H,
> RDI, RDI_H,
> RSI, RSI_H,
> RCX, RCX_H,
> @@ -226,9 +223,8 @@
> R13, R13_H,
> R14, R14_H);
>
> -// Class for all pointer registers except RAX, RBX and RSP
> +// Class for all pointer registers except RAX, RBX, RSP and RBP
> reg_class ptr_no_rax_rbx_reg(RDX, RDX_H,
> - RBP, RBP_H,
> RDI, RDI_H,
> RSI, RSI_H,
> RCX, RCX_H,
> @@ -260,10 +256,9 @@
> // Singleton class for TLS pointer
> reg_class ptr_r15_reg(R15, R15_H);
>
> -// Class for all long registers (except RSP)
> +// Class for all long registers (except RSP and RBP)
> reg_class long_reg(RAX, RAX_H,
> RDX, RDX_H,
> - RBP, RBP_H,
> RDI, RDI_H,
> RSI, RSI_H,
> RCX, RCX_H,
> @@ -275,9 +270,8 @@
> R13, R13_H,
> R14, R14_H);
>
> -// Class for all long registers except RAX, RDX (and RSP)
> -reg_class long_no_rax_rdx_reg(RBP, RBP_H,
> - RDI, RDI_H,
> +// Class for all long registers except RAX, RDX (and RSP, RBP)
> +reg_class long_no_rax_rdx_reg(RDI, RDI_H,
> RSI, RSI_H,
> RCX, RCX_H,
> RBX, RBX_H,
> @@ -288,9 +282,8 @@
> R13, R13_H,
> R14, R14_H);
>
> -// Class for all long registers except RCX (and RSP)
> -reg_class long_no_rcx_reg(RBP, RBP_H,
> - RDI, RDI_H,
> +// Class for all long registers except RCX (and RSP, RBP)
> +reg_class long_no_rcx_reg(RDI, RDI_H,
> RSI, RSI_H,
> RAX, RAX_H,
> RDX, RDX_H,
> @@ -302,9 +295,8 @@
> R13, R13_H,
> R14, R14_H);
>
> -// Class for all long registers except RAX (and RSP)
> -reg_class long_no_rax_reg(RBP, RBP_H,
> - RDX, RDX_H,
> +// Class for all long registers except RAX (and RSP, RBP)
> +reg_class long_no_rax_reg(RDX, RDX_H,
> RDI, RDI_H,
> RSI, RSI_H,
> RCX, RCX_H,
> @@ -325,10 +317,9 @@
> // Singleton class for RDX long register
> reg_class long_rdx_reg(RDX, RDX_H);
>
> -// Class for all int registers (except RSP)
> +// Class for all int registers (except RSP and RBP)
> reg_class int_reg(RAX,
> RDX,
> - RBP,
> RDI,
> RSI,
> RCX,
> @@ -340,10 +331,9 @@
> R13,
> R14);
>
> -// Class for all int registers except RCX (and RSP)
> +// Class for all int registers except RCX (and RSP, RBP)
> reg_class int_no_rcx_reg(RAX,
> RDX,
> - RBP,
> RDI,
> RSI,
> RBX,
> @@ -355,8 +345,7 @@
> R14);
>
> // Class for all int registers except RAX, RDX (and RSP)
> -reg_class int_no_rax_rdx_reg(RBP,
> - RDI,
> +reg_class int_no_rax_rdx_reg(RDI,
> RSI,
> RCX,
> RBX,
> @@ -718,6 +707,7 @@
> st->print("# stack bang");
> st->print("\n\t");
> st->print("pushq rbp\t# Save rbp");
> + // BDG consider: st->print("movq rbp, rsp\t# ");
> if (framesize) {
> st->print("\n\t");
> st->print("subq rsp, #%d\t# Create frame",framesize);
> --- openjdk8clean/hotspot/src/cpu/x86/vm/macroAssembler_x86.cpp
> 2014-03-04 02:52:11.000000000 +0000
> +++ openjdk8/hotspot/src/cpu/x86/vm/macroAssembler_x86.cpp 2014-11-07
> 23:57:11.589593723 +0000
> @@ -5236,6 +5236,7 @@
> // We always push rbp, so that on return to interpreter rbp, will be
> // restored correctly and we can correct the stack.
> push(rbp);
> + mov(rbp, rsp);
> // Remove word for ebp
> framesize -= wordSize;
>
> --- openjdk8clean/hotspot/src/cpu/x86/vm/c1_MacroAssembler_x86.cpp
> 2014-03-04 02:52:10.000000000 +0000
> +++ openjdk8/hotspot/src/cpu/x86/vm/c1_MacroAssembler_x86.cpp
> 2014-11-07 23:57:21.933257882 +0000
> @@ -358,6 +358,7 @@
> generate_stack_overflow_check(frame_size_in_bytes);
>
> push(rbp);
> + mov(rbp, rsp);
> #ifdef TIERED
> // c2 leaves fpu stack dirty. Clean it on entry
> if (UseSSE < 2 ) {
>
>
> Brendan
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