src,http2: refactor + generalize http2 debugging #20987

addaleax · 2018-05-27T15:24:47Z

tl;dr: Instead of having to compile with ./configure --debug-http2, get the same output with NODE_DEBUG_NATIVE=http2 node at runtime, in a way that makes implementing similar debugging for other core modules easier.

src: implement debug output utilities

Implement utilities for easier debugging of Node.js core code,
inspired by the HTTP/2 debugging code. Debugging is, however,
implemented at runtime rather than at compile time, controlled
through a new through a new NODE_DEBUG_NATIVE=categories
environment variable.

The runtime overhead in the debugging-disabled case amounts to
1 well-cachable one-byte read per debug call.
http2: switch to new runtime-controlled debugging system

Remove --debug-http2 as a compile-time feature and
make all debug statements available using NODE_DEBUG_NATIVE=http2
at runtime.

This probably makes the debugging-enabled case a bit slower due to
additional string concatenations, but switching to a runtime-checking
system makes debugging more flexible and can be applied more easily
to other parts of the source code as well.

Checklist

make -j4 test (UNIX), or vcbuild test (Windows) passes
tests and/or benchmarks are included
commit message follows commit guidelines

addaleax · 2018-05-27T15:26:08Z

CI: https://ci.nodejs.org/job/node-test-commit/18805/
Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/202/

benjamingr · 2018-05-27T15:29:18Z

src/util-inl.h

@@ -293,6 +293,13 @@ char ToLower(char c) {
  return c >= 'A' && c <= 'Z' ? c + ('a' - 'A') : c;
 }

+std::string ToLower(const std::string& in) {


Random unrelated questions - since we always build with an ICU - isn't this the sort of thing the ICU can do?

Also - is the loop below not a for(auto elm : in) due to stylistic preference or something else?

isn't this the sort of thing the ICU can do?

No idea – doing it this way doesn’t cost us much though, though. @srl295 probably has a more helpful answer :)

Also - is the loop below not a for(auto elm : in) due to stylistic preference or something else?

We’d probably still want to set the characters in the output string directly rather than appending them one at a time, so we’d want to maintain an index for that. In those cases, yes, I prefer to use the explicit index for the input as well, even though we could do it without. :)

joyeecheung · 2018-05-27T15:41:08Z

We have the NODE_DEBUG environment variable for this and it's documented. Any reason to introduce a new command line flag?

addaleax · 2018-05-27T15:43:08Z

@joyeecheung Nothing besides that this works slightly differently (currently category names correspond to AsyncWrap types rather than core modules) and that it targets the C++ layer rather than the JS layer. If you think we should re-use NODE_DEBUG here, that’s not an issue for me. :)

joyeecheung · 2018-05-27T15:47:48Z

@addaleax I am OK if the flag is dedicated for debugging output from the C++ side, as far as I know the environment variable is only honored in the JS land. But if we provide two mechanisms to achieve a similar purpose it would be rather confusing.

mscdex · 2018-05-27T15:51:19Z

src/env.cc

+      break;
+    // Use everything after the `,` as the list for the next iteration.
+    debug_categories =
+        debug_categories.substr(comma_pos);


Why is this on a new line?

Because the line was originally a bit longer. Fixed! :)

Implement utilities for easier debugging of Node.js core code, inspired by the HTTP/2 debugging code. Debugging is, however, implemented at runtime rather than at compile time, controlled through a new `NODE_DEBUG_NATIVE=categories` environment variable. The runtime overhead in the debugging-disabled case amounts to 1 well-cachable one-byte read per debug call.

addaleax · 2018-05-27T19:12:43Z

@joyeecheung I’ve switched this to use NODE_DEBUG_NATIVE as an environment variable – if you want, I can fully merge with NODE_DEBUG (atm the categories and the parsing are still different for the two). Does that sound okay?

addaleax · 2018-05-27T20:11:30Z

The benchmark machine still doesn’t have h2load, but I ran HTTP/2 benchmarks locally and saw a -3 % regression in some of them. I’ve added hints to the compiler, so that it generates more sensible code in terms of inlining and register pressure … not a pretty solution, but the benchmarks seem better now (will post the full results as soon as I have them).

CI: https://ci.nodejs.org/job/node-test-commit/18808/

Remove `--debug-http2` as a compile-time feature and make all debug statements available using `NODE_DEBUG_NATIVE=http2` at runtime. This probably makes the debugging-enabled case a bit slower due to additional string concatenations, but switching to a runtime-checking system makes debugging more flexible and can be applied more easily to other parts of the source code as well.

addaleax · 2018-05-27T23:16:27Z

Benchmark results now look the way we want them to:

Output in the fold

$ Rscript benchmark/compare.R < 20987.benchmark 
                                                                                      confidence improvement accuracy (*)    (**)   (***)
 http2/headers.js benchmarker='h2load' nheaders=0 n=1000                                              0.75 %       ±0.76%  ±1.01%  ±1.31%
 http2/headers.js benchmarker='h2load' nheaders=1000 n=1000                                           0.31 %       ±0.64%  ±0.86%  ±1.11%
 http2/headers.js benchmarker='h2load' nheaders=100 n=1000                                            0.12 %       ±0.64%  ±0.85%  ±1.11%
 http2/headers.js benchmarker='h2load' nheaders=10 n=1000                                     **      1.01 %       ±0.68%  ±0.91%  ±1.18%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=1000 requests=100                   -0.10 %       ±2.39%  ±3.18%  ±4.14%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=1000 requests=1000                   0.81 %       ±2.21%  ±2.94%  ±3.83%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=1000 requests=10000                  1.41 %       ±2.43%  ±3.23%  ±4.21%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=1000 requests=100000                -0.07 %       ±1.72%  ±2.29%  ±2.98%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=100 requests=100                    -0.26 %       ±1.69%  ±2.25%  ±2.93%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=100 requests=1000                    0.04 %       ±1.99%  ±2.65%  ±3.45%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=100 requests=10000                   1.07 %       ±2.16%  ±2.87%  ±3.74%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=100 requests=100000                  0.61 %       ±1.96%  ±2.61%  ±3.40%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=200 requests=100                     0.48 %       ±1.98%  ±2.64%  ±3.44%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=200 requests=1000                    0.95 %       ±1.94%  ±2.58%  ±3.35%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=200 requests=10000                   0.50 %       ±2.14%  ±2.85%  ±3.71%
 http2/respond-with-fd.js benchmarker='h2load' clients=1 streams=200 requests=100000                  0.29 %       ±1.58%  ±2.11%  ±2.74%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=1000 requests=100                   -1.11 %       ±2.50%  ±3.33%  ±4.33%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=1000 requests=1000                   0.35 %       ±1.45%  ±1.93%  ±2.52%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=1000 requests=10000           *      1.77 %       ±1.72%  ±2.28%  ±2.97%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=1000 requests=100000                 0.30 %       ±1.48%  ±1.97%  ±2.56%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=100 requests=100                     0.95 %       ±2.47%  ±3.29%  ±4.29%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=100 requests=1000                    0.90 %       ±1.63%  ±2.17%  ±2.83%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=100 requests=10000                   1.10 %       ±1.65%  ±2.19%  ±2.85%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=100 requests=100000                  0.89 %       ±1.52%  ±2.02%  ±2.63%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=200 requests=100                     1.32 %       ±2.60%  ±3.46%  ±4.50%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=200 requests=1000             *      1.78 %       ±1.39%  ±1.85%  ±2.41%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=200 requests=10000                   0.07 %       ±1.60%  ±2.13%  ±2.77%
 http2/respond-with-fd.js benchmarker='h2load' clients=2 streams=200 requests=100000                  0.24 %       ±1.19%  ±1.59%  ±2.07%
 http2/simple.js benchmarker='h2load' clients=1 streams=1000 requests=100                            -1.40 %       ±6.87%  ±9.39% ±12.74%
 http2/simple.js benchmarker='h2load' clients=1 streams=1000 requests=1000                            0.77 %       ±2.21%  ±3.01%  ±4.07%
 http2/simple.js benchmarker='h2load' clients=1 streams=1000 requests=10000                          -0.16 %       ±2.26%  ±3.09%  ±4.18%
 http2/simple.js benchmarker='h2load' clients=1 streams=1000 requests=100000                         -0.21 %       ±2.70%  ±3.69%  ±4.99%
 http2/simple.js benchmarker='h2load' clients=1 streams=100 requests=100                              1.70 %       ±7.41% ±10.13% ±13.75%
 http2/simple.js benchmarker='h2load' clients=1 streams=100 requests=1000                            -0.39 %       ±2.08%  ±2.85%  ±3.88%
 http2/simple.js benchmarker='h2load' clients=1 streams=100 requests=10000                            0.77 %       ±1.84%  ±2.55%  ±3.55%
 http2/simple.js benchmarker='h2load' clients=1 streams=100 requests=100000                           0.57 %       ±2.32%  ±3.16%  ±4.28%
 http2/simple.js benchmarker='h2load' clients=1 streams=200 requests=100                              4.38 %       ±7.54% ±10.33% ±14.08%
 http2/simple.js benchmarker='h2load' clients=1 streams=200 requests=1000                            -1.61 %       ±2.65%  ±3.62%  ±4.89%
 http2/simple.js benchmarker='h2load' clients=1 streams=200 requests=10000                           -0.52 %       ±2.40%  ±3.27%  ±4.43%
 http2/simple.js benchmarker='h2load' clients=1 streams=200 requests=100000                    *     -2.25 %       ±2.25%  ±3.07%  ±4.15%
 http2/simple.js benchmarker='h2load' clients=2 streams=1000 requests=100                            -3.38 %       ±5.65%  ±7.70% ±10.43%
 http2/simple.js benchmarker='h2load' clients=2 streams=1000 requests=1000                            0.72 %       ±2.60%  ±3.55%  ±4.82%
 http2/simple.js benchmarker='h2load' clients=2 streams=1000 requests=10000                          -0.30 %       ±1.93%  ±2.66%  ±3.65%
 http2/simple.js benchmarker='h2load' clients=2 streams=1000 requests=100000                          0.92 %       ±1.64%  ±2.26%  ±3.08%
 http2/simple.js benchmarker='h2load' clients=2 streams=100 requests=100                             -2.94 %       ±8.55% ±11.70% ±15.90%
 http2/simple.js benchmarker='h2load' clients=2 streams=100 requests=1000                             0.58 %       ±2.83%  ±3.88%  ±5.28%
 http2/simple.js benchmarker='h2load' clients=2 streams=100 requests=10000                           -0.10 %       ±1.85%  ±2.54%  ±3.49%
 http2/simple.js benchmarker='h2load' clients=2 streams=100 requests=100000                           0.37 %       ±1.57%  ±2.14%  ±2.89%
 http2/simple.js benchmarker='h2load' clients=2 streams=200 requests=100                             -0.55 %       ±6.85%  ±9.35% ±12.65%
 http2/simple.js benchmarker='h2load' clients=2 streams=200 requests=1000                             0.54 %       ±3.15%  ±4.31%  ±5.86%
 http2/simple.js benchmarker='h2load' clients=2 streams=200 requests=10000                            0.42 %       ±2.03%  ±2.77%  ±3.75%
 http2/simple.js benchmarker='h2load' clients=2 streams=200 requests=100000                           0.04 %       ±1.46%  ±1.99%  ±2.70%

Be aware that when doing many comparisions the risk of a false-positive
result increases. In this case there are 52 comparisions, you can thus
expect the following amount of false-positive results:
  2.60 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.52 false positives, when considering a   1% risk acceptance (**, ***),
  0.05 false positives, when considering a 0.1% risk acceptance (***)

benjamingr · 2018-05-28T08:16:43Z

Can someone explain to me why the benchmark tool is confident that this improves performance by 1% in that benchmark? I don't see any changes that should do that but I don't know the http2 code well at all :)

addaleax · 2018-05-28T09:59:40Z

@benjamingr I’d expect it to be one of the 0.52 false positives we should expect. Running that benchmark more frequently shows no significant change:

$ ./node benchmark/compare.js --new ./node --old ./node-master --runs 180 --filter headers --set nheaders=10 --set n=1000 http2 | Rscript benchmark/compare.R
[00:04:08|% 100| 1/1 files | 360/360 runs | 1/1 configs]: Done
                                                           confidence improvement accuracy (*)   (**)  (***)
 http2/headers.js benchmarker='h2load' nheaders=10 n=1000                 0.14 %       ±0.33% ±0.43% ±0.56%

joyeecheung · 2018-05-28T10:08:19Z

@benjamingr It could be just fluctuations

benjamingr · 2018-05-28T11:26:16Z

Ok, thanks for clarifying - maybe we should add a guide for how to read significance in the benchmark output. I've considered ** as high confidence before.

addaleax · 2018-05-29T22:15:09Z

CI: https://ci.nodejs.org/job/node-test-commit/18860/

addaleax · 2018-05-31T08:01:27Z

Landed in bd85844, 15c7a49

Implement utilities for easier debugging of Node.js core code, inspired by the HTTP/2 debugging code. Debugging is, however, implemented at runtime rather than at compile time, controlled through a new `NODE_DEBUG_NATIVE=categories` environment variable. The runtime overhead in the debugging-disabled case amounts to 1 well-cachable one-byte read per debug call. PR-URL: #20987 Reviewed-By: Daniel Bevenius <[email protected]> Reviewed-By: Joyee Cheung <[email protected]> Reviewed-By: Minwoo Jung <[email protected]> Reviewed-By: James M Snell <[email protected]>

Remove `--debug-http2` as a compile-time feature and make all debug statements available using `NODE_DEBUG_NATIVE=http2` at runtime. This probably makes the debugging-enabled case a bit slower due to additional string concatenations, but switching to a runtime-checking system makes debugging more flexible and can be applied more easily to other parts of the source code as well. PR-URL: #20987 Reviewed-By: Daniel Bevenius <[email protected]> Reviewed-By: Joyee Cheung <[email protected]> Reviewed-By: Minwoo Jung <[email protected]> Reviewed-By: James M Snell <[email protected]>

Implement utilities for easier debugging of Node.js core code, inspired by the HTTP/2 debugging code. Debugging is, however, implemented at runtime rather than at compile time, controlled through a new `NODE_DEBUG_NATIVE=categories` environment variable. The runtime overhead in the debugging-disabled case amounts to 1 well-cachable one-byte read per debug call. PR-URL: #20987 Reviewed-By: Daniel Bevenius <[email protected]> Reviewed-By: Joyee Cheung <[email protected]> Reviewed-By: Minwoo Jung <[email protected]> Reviewed-By: James M Snell <[email protected]>

Remove `--debug-http2` as a compile-time feature and make all debug statements available using `NODE_DEBUG_NATIVE=http2` at runtime. This probably makes the debugging-enabled case a bit slower due to additional string concatenations, but switching to a runtime-checking system makes debugging more flexible and can be applied more easily to other parts of the source code as well. PR-URL: #20987 Reviewed-By: Daniel Bevenius <[email protected]> Reviewed-By: Joyee Cheung <[email protected]> Reviewed-By: Minwoo Jung <[email protected]> Reviewed-By: James M Snell <[email protected]>

- nodejs/node#21238 - nodejs/node#20987

addaleax requested a review from jasnell May 27, 2018 15:24

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. lib / src Issues and PRs related to general changes in the lib or src directory. labels May 27, 2018

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addaleax force-pushed the re-debug branch from 9e76960 to f9f234d Compare May 27, 2018 19:12

[squash] be more active about telling the compiler what to do

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addaleax added 2 commits May 27, 2018 23:19

[squash] fix linter error

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why is it so hard to add threads to nodejs? or web workers? nodejs/worker#4

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MylesBorins mentioned this pull request Jun 6, 2018

v10.4.0 proposal #21167

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fixup! chore: add GN build files

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- nodejs/node#21238 - nodejs/node#20987

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[8.x] Backport http2 changes from 10.x #22850

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http2: simplify timeout tracking #19206

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src,http2: refactor + generalize http2 debugging #20987

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src,http2: refactor + generalize http2 debugging #20987

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