loader: speed up line length calculation used by moduleProvider #50969

zeusdeux · 2023-11-29T22:02:05Z

When using a loader, for e.g., say TypeScript, the esm loader invokes the lineLengths function via maybeCacheSourceMap when sourcemaps are enabled. Therefore, lineLengths ends up getting called quite often when running large servers written in TypeScript for example. Making lineLengths faster should therefore speed up server startup times for anyone using a loader with node with sourcemaps enabled.

The change itself is fairly simple and is all about removing creation of unnecessary memory and iterating the whole source content only once with the hope of making the function cache friendly.

make -j4 test passes

Alongside that, below are the cpuprofiles of node 20.9.0 vs node main with this patch taken during the startup of large server (from work) written in TypeScript loaded using esno (a proxy to esbuild-register) showing a ~98% reduction in time taken by moduleProvider.

node 20.9.0

node `main` + patch from this PR

zeusdeux · 2023-11-29T22:42:07Z

Pinging the modules team since the loaders WG readme doesn't mention who is in it (apologies if you aren't working on loaders but got pinged here 🙏🏽 ).
@bmeck, @DanielRosenwasser, @devsnek, @GeoffreyBooth, @giltayar, @guybedford, @JakobJingleheimer, @jkrems, @ljharb, @MylesBorins, @qballer, @robpalme, @targos, @VoltrexKeyva, @WebReflection, @weswigham, @zackschuster

GeoffreyBooth · 2023-11-29T22:43:53Z

Next time please just ping @nodejs/loaders. cc @nodejs/performance

zeusdeux · 2023-11-29T22:48:24Z

Ah so those teams do exist! I assumed they didn't as the autocomplete here didn't show them. 🤦🏽‍♂️
Thanks for the pointer @GeoffreyBooth 🙏🏽

lib/internal/source_map/source_map_cache.js

ljharb · 2023-11-29T22:52:14Z

lib/internal/source_map/source_map_cache.js

+    // account in coverage calculations.
+    // codepoints for \n, \u2028 and \u2029
+    if (codePoint === 10 || codePoint === 0x2028 || codePoint === 0x2029) {
+      output.push(lineLength);


Suggested change

output.push(lineLength);

ArrayPrototypePush(output, lineLength);

ljharb · 2023-11-29T22:52:22Z

lib/internal/source_map/source_map_cache.js

+      lineLength = -1; // To not count the matched codePoint such as \n character
+    }
+  }
+  output.push(lineLength);


Suggested change

output.push(lineLength);

ArrayPrototypePush(output, lineLength);

ArrayPrototypePush has performance implications according to primordials.md. Since adding primordials is optional, I'm strongly against adding it for array.prototype.push in this PR.

I think for source map support, we don't want user code to be able to mess with internal implementation – i.e. we should take the potential performance penalty and generate reliably correct stack traces. Also, we should measure the perf difference, as it might be negligable.

alternatively, output[output.length] = lineLength?

nodejs-github-bot · 2023-11-29T22:54:10Z

CI: https://ci.nodejs.org/job/node-test-pull-request/56011/

lib/internal/source_map/source_map_cache.js

GeoffreyBooth · 2023-11-29T22:52:19Z

lib/internal/source_map/source_map_cache.js

+      lineLength = -1; // To not count the matched codePoint such as \n character
+    }
+  }
+  output.push(lineLength);


Suggested change

output.push(lineLength);

ArrayPrototypePush(output, lineLength);

lib/internal/source_map/source_map_cache.js

aduh95 · 2023-11-29T23:05:33Z

lib/internal/source_map/source_map_cache.js

+    // account in coverage calculations.
+    // codepoints for \n (new line), \u2028 (line separator) and \u2029 (paragraph separator)
+    if (codePoint === 10 || codePoint === 0x2028 || codePoint === 0x2029) {
+      output.push(lineLength)


Suggested change

output.push(lineLength)

ArrayPrototypePush(output, lineLength);

zeusdeux · 2023-11-29T23:05:56Z

lib/internal/source_map/source_map_cache.js

+    // account in coverage calculations.
+    // codepoints for \n (new line), \u2028 (line separator) and \u2029 (paragraph separator)
+    if (codePoint === 10 || codePoint === 0x2028 || codePoint === 0x2029) {
+      output.push(lineLength)


Using the non-primordial version due to ArrayPrototypePush being listed as having perf issues — https://github.com/nodejs/node/blob/main/doc/contributing/primordials.md#primordials-with-known-performance-issues

aduh95 · 2023-11-29T23:06:00Z

lib/internal/source_map/source_map_cache.js

+      lineLength = -1; // To not count the matched codePoint such as \n character
+    }
+  }
+  output.push(lineLength)


Suggested change

output.push(lineLength)

ArrayPrototypePush(output, lineLength);

ArrayPrototypePush has known perf issues — #50969 (comment)

Using .push has reliability issues, as user code could affect internals.

zeusdeux · 2023-11-29T23:45:15Z

@aduh95 @GeoffreyBooth @anonrig What's the call on the usage of .push vs ArrayPrototypePush from the perspective of correctness as brought up by @aduh95? Should I invest time on measuring the perf impact or is .push ok as is?

anonrig · 2023-11-29T23:56:44Z

@zeusdeux Primordials are optional and not mandatory for new pull requests. It's your decision.

Documentation says that:

Usage of primordials should be preferred for any new code...

Ref: https://github.com/nodejs/node/blob/main/doc/contributing/primordials.md

GeoffreyBooth · 2023-11-30T00:10:30Z

@aduh95 @GeoffreyBooth @anonrig What’s the call on the usage of .push vs ArrayPrototypePush from the perspective of correctness as brought up by @aduh95?

I don’t have a preference. I thought we were still debating whether they should be required, but I don’t really see the need.

When using a loader, for say TypeScript, the esm loader invokes the `lineLengths` function via `maybeCacheSourceMap` when sourcemaps are enabled. Therefore, `lineLengths` ends up getting called quite often when running large servers written in TypeScript for example. Making `lineLengths` faster should therefore speed up server startup times for anyone using a loader with node with sourcemaps enabled. The change itself is fairly simple and is all about removing creation of unnecessary memory and iterating the whole source content only once with the hope of making the function cache friendly.

zeusdeux · 2023-11-30T01:26:06Z

I went ahead and did 4 runs of the same test as in the perf profile screenshots in the original PR description. Using ArrayPrototypePush seems to shave off another ~8ms for an average of ~72ms across the four runs. I have therefore updated the PR to use it as we get both safety and speed in my preliminary tests.

Process for testing:

update the code to use ArrayPrototypePush
recompile node
link to the release binary
run server under test
take a cpuprofile x 4

Example run

GeoffreyBooth · 2023-11-30T04:06:01Z

Using ArrayPrototypePush seems to shave off

If you're going to use that one you might as well use the others too?

ljharb

looks great, robustness > performance, altho even better if we can get both.

you may want to benchmark arr[arr.length] = x over ArrayPrototypePush(arr, x) just in case tho

aduh95

Great to hear we can reconcile robustness and perf. Ideally we would run benchmarks after each V8 upgrades to see if the claims in primordials.md are still correct, but it's very time consuming, and easy to get false positive.

If you want to check the performance of arr[arr.length] = value and setOwnProperty(arr, arr.length, value) for completeness, that'd be useful data.

zeusdeux · 2023-11-30T10:21:41Z

@GeoffreyBooth which other ones? This PR uses StringPrototypeCodePointAt and ArrayPrototypePush already.
As for the completeness aspect @ljharb @aduh95, I can do that post landing perhaps as the time spent per run of data collection is quite high.

aduh95 · 2023-11-30T10:29:56Z

✘ This PR needs to wait 35 more hours to land

Sure, whatever works for you. But FYI this PR needs to wait at least 48 hours after it was opened before we can merge it to give time for folks to review, so it may be quicker to get the data before the PR is merged depending on what are your availabilities.

nodejs-github-bot · 2023-12-01T22:08:49Z

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- Loading data for nodejs/node/pull/50969
✔  Done loading data for nodejs/node/pull/50969
----------------------------------- PR info ------------------------------------
Title      loader: speed up line length calculation used by moduleProvider (#50969)
Author     Mudit  (@zeusdeux)
Branch     zeusdeux:speed-up-source-map-processing -> nodejs:main
Labels     module, performance, needs-ci, source maps
Commits    1
 - loader: speed up line length calc used by moduleProvider
Committers 1
 - Mudit Ameta 
PR-URL: https://github.com/nodejs/node/pull/50969
Reviewed-By: Yagiz Nizipli 
Reviewed-By: Geoffrey Booth 
Reviewed-By: Antoine du Hamel 
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/50969
Reviewed-By: Yagiz Nizipli 
Reviewed-By: Geoffrey Booth 
Reviewed-By: Antoine du Hamel 
--------------------------------------------------------------------------------
   ℹ  This PR was created on Wed, 29 Nov 2023 22:02:05 GMT
   ✔  Approvals: 3
   ✔  - Yagiz Nizipli (@anonrig) (TSC): https://github.com/nodejs/node/pull/50969#pullrequestreview-1758724448
   ✔  - Geoffrey Booth (@GeoffreyBooth) (TSC): https://github.com/nodejs/node/pull/50969#pullrequestreview-1756426036
   ✔  - Antoine du Hamel (@aduh95) (TSC): https://github.com/nodejs/node/pull/50969#pullrequestreview-1757049826
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   ℹ  Last Full PR CI on 2023-11-29T22:54:10Z: https://ci.nodejs.org/job/node-test-pull-request/56011/
   ⚠  Commits were pushed after the last Full PR CI run:
   ⚠  - loader: speed up line length calc used by moduleProvider
- Querying data for job/node-test-pull-request/56011/
   ✔  Last Jenkins CI successful
--------------------------------------------------------------------------------
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https://github.com/nodejs/node/actions/runs/7065693910

nodejs-github-bot · 2023-12-02T00:23:56Z

CI: https://ci.nodejs.org/job/node-test-pull-request/56043/

JakobJingleheimer

Huzzah 🙌 Thanks for this!

Out of curiosity, where did the huge perf gain come from? arr.map → for, or RegExp → equality assertion, or both significantly contributed? (I would guess both)

nodejs-github-bot · 2023-12-02T13:53:07Z

Landed in d5a7acf

zeusdeux · 2023-12-03T00:43:43Z

@JakobJingleheimer Thanks! The speed up was from the combination of the following —

Not allocating new memory for the regex and not trampolining to the regex constructor
Not allocating new memory for the function given to map and thus its whole closure
Not trampolining between map and the fn it calls per item
Only traversing the string content once linearly with no side effects to it thus making it cache line friendly
Doing simple math in a for loop that all compilers are extremely good at optimizing (for loops/while/do while will always beat perf of for of, map and friends)

Basically doing only what's needed and doing it using an known optimizable construct. Finally, no extra memory overhead than absolutely necessary. Thinking in C rather than JS in a way.

Functional programming is good but it's usually horrible for perf so going old school for parts that are sensitive to perf is always a win!

When using a loader, for say TypeScript, the esm loader invokes the `lineLengths` function via `maybeCacheSourceMap` when sourcemaps are enabled. Therefore, `lineLengths` ends up getting called quite often when running large servers written in TypeScript for example. Making `lineLengths` faster should therefore speed up server startup times for anyone using a loader with node with sourcemaps enabled. The change itself is fairly simple and is all about removing creation of unnecessary memory and iterating the whole source content only once with the hope of making the function cache friendly. PR-URL: #50969 Reviewed-By: Yagiz Nizipli <yagiz.nizipli@sentry.io> Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com> Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Vinícius Lourenço Claro Cardoso <contact@viniciusl.com.br> Reviewed-By: Jacob Smith <jacob@frende.me>

nodejs-github-bot added the needs-ci PRs that need a full CI run. label Nov 29, 2023

zeusdeux changed the title ~~loader: Speed up line length calculation used by moduleProvider~~ loader: speed up line length calculation used by moduleProvider Nov 29, 2023

zeusdeux force-pushed the speed-up-source-map-processing branch 2 times, most recently from 172138f to 686ce4e Compare November 29, 2023 22:10

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loader: speed up line length calculation used by moduleProvider #50969

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	output.push(lineLength);
	ArrayPrototypePush(output, lineLength);

	output.push(lineLength)
	ArrayPrototypePush(output, lineLength);

loader: speed up line length calculation used by moduleProvider #50969

loader: speed up line length calculation used by moduleProvider #50969

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zeusdeux commented Nov 29, 2023 • edited Loading

node 20.9.0

node main + patch from this PR

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Example run

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node `main` + patch from this PR

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