RFR: 8178287: AsyncGetCallTrace fails to traverse valid Java stacks

[Serguei Spitsyn]

On Wed, 9 Jun 2021 17:16:23 GMT, Ludovic Henry <luhenry at openjdk.org> wrote:

> When the signal sent for AsyncGetCallTrace or JFR would land on a runtime stub (like arraycopy), a vtable stub, or the prolog of a compiled method,  it wouldn't be able to detect the sender (caller) frame for multiple reasons. This patch fixes these cases through adding CodeBlob-specific frame parser which are in the best position to know how a frame is setup.
> 
> The following examples have been profiled with honest-profiler which uses `AsyncGetCallTrace`.
> 
> # `Prof1`
> 
> public class Prof1 {
> 
>     public static void main(String[] args) {
>         StringBuilder sb = new StringBuilder();
>         for (int i = 0; i < 1000000; i++) {
>             sb.append("ab");
>             sb.delete(0, 1);
>         }
>         System.out.println(sb.length());
>     }
> }
> 
> 
> - Baseline:
> 
> Flat Profile (by method):
>         (t 99.4,s 99.4) AGCT::Unknown Java[ERR=-5]
>         (t  0.5,s  0.2) Prof1::main
>         (t  0.2,s  0.2) java.lang.AbstractStringBuilder::append
>         (t  0.1,s  0.1) AGCT::Unknown not Java[ERR=-3]
>         (t  0.0,s  0.0) java.lang.AbstractStringBuilder::ensureCapacityInternal
>         (t  0.0,s  0.0) java.lang.AbstractStringBuilder::shift
>         (t  0.0,s  0.0) java.lang.String::getBytes
>         (t  0.0,s  0.0) java.lang.AbstractStringBuilder::putStringAt
>         (t  0.0,s  0.0) java.lang.StringBuilder::delete
>         (t  0.2,s  0.0) java.lang.StringBuilder::append
>         (t  0.0,s  0.0) java.lang.AbstractStringBuilder::delete
>         (t  0.0,s  0.0) java.lang.AbstractStringBuilder::putStringAt
> 
> - With `StubRoutinesBlob::FrameParser`:
> 
> Flat Profile (by method):
>         (t 98.7,s 98.7) java.lang.AbstractStringBuilder::ensureCapacityInternal
>         (t  0.9,s  0.9) java.lang.AbstractStringBuilder::delete
>         (t 99.8,s  0.2) Prof1::main
>         (t  0.1,s  0.1) AGCT::Unknown not Java[ERR=-3]
>         (t  0.0,s  0.0) AGCT::Unknown Java[ERR=-5]
>         (t 98.8,s  0.0) java.lang.AbstractStringBuilder::append
>         (t 98.8,s  0.0) java.lang.StringBuilder::append
>         (t  0.9,s  0.0) java.lang.StringBuilder::delete
> 
> 
> # `Prof2`
> 
> import java.util.function.Supplier;
> 
> public class Prof2 {
> 
>     public static void main(String[] args) {
>         var rand = new java.util.Random(0);
>         Supplier[] suppliers = {
>                 () -> 0,
>                 () -> 1,
>                 () -> 2,
>                 () -> 3,
>         };
> 
>         long sum = 0;
>         for (int i = 0; i >= 0; i++) {
>             sum += (int)suppliers[i % suppliers.length].get();
>         }
>     }
> }
> 
> 
> - Baseline:
> 
> Flat Profile (by method):
>         (t 60.7,s 60.7) AGCT::Unknown Java[ERR=-5]
>         (t 39.2,s 35.2) Prof2::main
>         (t  1.4,s  1.4) Prof2::lambda$main$3
>         (t  1.0,s  1.0) Prof2::lambda$main$2
>         (t  0.9,s  0.9) Prof2::lambda$main$1
>         (t  0.7,s  0.7) Prof2::lambda$main$0
>         (t  0.1,s  0.1) AGCT::Unknown not Java[ERR=-3]
>         (t  0.0,s  0.0) java.lang.Thread::exit
>         (t  0.9,s  0.0) Prof2$$Lambda$2.0x0000000800c00c28::get
>         (t  1.0,s  0.0) Prof2$$Lambda$3.0x0000000800c01000::get
>         (t  1.4,s  0.0) Prof2$$Lambda$4.0x0000000800c01220::get
>         (t  0.7,s  0.0) Prof2$$Lambda$1.0x0000000800c00a08::get
> 
> 
> - With `VtableBlob::FrameParser` and `nmethod::FrameParser`:
> 
> Flat Profile (by method):
>         (t 74.1,s 70.3) Prof2::main
>         (t  6.5,s  5.5) Prof2$$Lambda$29.0x0000000800081220::get
>         (t  6.6,s  5.4) Prof2$$Lambda$28.0x0000000800081000::get
>         (t  5.7,s  5.0) Prof2$$Lambda$26.0x0000000800080a08::get
>         (t  5.9,s  5.0) Prof2$$Lambda$27.0x0000000800080c28::get
>         (t  4.9,s  4.9) AGCT::Unknown Java[ERR=-5]
>         (t  1.2,s  1.2) Prof2::lambda$main$2
>         (t  0.9,s  0.9) Prof2::lambda$main$3
>         (t  0.9,s  0.9) Prof2::lambda$main$1
>         (t  0.7,s  0.7) Prof2::lambda$main$0
>         (t  0.1,s  0.1) AGCT::Unknown not Java[ERR=-3]

Hi Ludovic,
Thank you for working on this fix in the AsyncGetCallTrace.
What version of JDK release do you intent to target?
Just wanted to make sure you know the JDK 17 development cycle will be closed tomorrow for P4 bugs and enhancements. The repository will be forked and the RDP 1 phase started.
I doubt the review of your fix will be completed by this time.
So, please, keep in mind your PR will go to 18, not 17.
Thanks,
Serguei

-------------

PR: https://git.openjdk.java.net/jdk/pull/4436