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List:       openjdk-serviceability-dev
Subject:    Re: RFR: 8178287: AsyncGetCallTrace fails to traverse valid Java stacks [v3]
From:       Serguei Spitsyn <sspitsyn () openjdk ! java ! net>
Date:       2021-06-30 9:21:05
Message-ID: eebr3nRX7hK2JWexDfv8WJD4f6w-YzBPZ-A2ps3RquU=.1b6132d6-0c47-4b07-9e66-e1563b2b0b5c () github ! com
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On Fri, 18 Jun 2021 08:56:32 GMT, Ludovic Henry <luhenry@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]
> 
> Ludovic Henry has updated the pull request incrementally with one additional commit \
> since the last revision: 
> Fix comments

Hi Ludovic,
You need two reviews including one (R)eviewer before integration of your fix.
Thanks,
Serguei

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

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


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