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GeezerVison is showing github.com — src: fix performance regression in node_file.cc by bnoordhuis · Pull Request #31343 · nodejs/node

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@bnoordhuis

@bnoordhuis bnoordhuis commented Jan 13, 2020

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Commits dcb6929, 4396beb and 8a96d05 turned the O(n) scan in
InternalModuleReadJSON() into an O(4n) scan. Fix the performance
regression by turning that into a linear scan again.

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@nodejs-github-bot nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. fs Issues and PRs related to file-system APIs and the fs module. labels Jan 13, 2020
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nodejs-github-bot commented Jan 13, 2020

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CI: https://ci.nodejs.org/job/node-test-pull-request/28431/
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cjihrig
cjihrig approved these changes Jan 13, 2020
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guybedford
guybedford approved these changes Jan 13, 2020
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Great to see this, thanks.

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devnexen
devnexen approved these changes Jan 13, 2020
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devsnek
devsnek reviewed Jan 13, 2020
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Comment thread src/node_file.cc Outdated

@devsnek devsnek Jan 13, 2020

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could you use if statements here to avoid goto?

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@bnoordhuis bnoordhuis Jan 14, 2020

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No, for two reasons:

  1. Aesthetic. It keeps the level of indent small.
  2. Performance. g++ 9.2.1 at -O3 doesn't move the block out of the way. The goto keeps the inner loop at around 80 bytes:
Details 
    10ec:       80 f9 22                cmp    $0x22,%cl
    10ef:       74 1f                   je     1110 <main+0x70>
    10f1:       80 f9 5c                cmp    $0x5c,%cl
    10f4:       75 44                   jne    113a <main+0x9a>
    10f6:       48 39 fa                cmp    %rdi,%rdx
    10f9:       73 65                   jae    1160 <main+0xc0>
    10fb:       0f b6 4e 01             movzbl 0x1(%rsi),%ecx
    10ff:       80 f9 22                cmp    $0x22,%cl
    1102:       74 7c                   je     1180 <main+0xe0>
    1104:       48 89 d6                mov    %rdx,%rsi
    1107:       48 8d 56 01             lea    0x1(%rsi),%rdx
    110b:       80 f9 22                cmp    $0x22,%cl
    110e:       75 e1                   jne    10f1 <main+0x51>
    1110:       49 8d 48 08             lea    0x8(%r8),%rcx
    1114:       49 89 10                mov    %rdx,(%r8)
    1117:       4c 39 c9                cmp    %r9,%rcx
    111a:       72 34                   jb     1150 <main+0xb0>
    111c:       48 8b 34 24             mov    (%rsp),%rsi
    1120:       48 89 f1                mov    %rsi,%rcx
    1123:       48 f7 d1                not    %rcx
    1126:       48 03 4c 24 08          add    0x8(%rsp),%rcx
    112b:       48 83 f9 04             cmp    $0x4,%rcx
    112f:       74 5f                   je     1190 <main+0xf0>
    1131:       4d 89 d0                mov    %r10,%r8
    1134:       48 83 f9 07             cmp    $0x7,%rcx
    1138:       74 76                   je     11b0 <main+0x110>
    113a:       48 39 fa                cmp    %rdi,%rdx
    113d:       73 21                   jae    1160 <main+0xc0>
    113f:       0f b6 0a                movzbl (%rdx),%ecx
    1142:       48 89 d6                mov    %rdx,%rsi
    1145:       eb a1                   jmp    10e8 <main+0x48>

(-O3 is kind of disappointing; with -Os it fits in a single cache line.)

I'll add a comment explaining why it's there.

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addaleax
addaleax approved these changes Jan 13, 2020
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Code LGTM but the commit message should be changed to something that’s a) descriptive of what this commit actually does and b) not a wordplay on a right-wing slogan before or during merging.

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ryanmurakami
ryanmurakami previously requested changes Jan 13, 2020
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@bnoordhuis The Moderation Team is requesting that you change the commit message and pull request title. The Moderation Team believes the similarities to an American politician's campaign slogan is not in line with the Code of Conduct's guide to use "welcoming and inclusive language". The Moderation Team is happy to provide external references should you need them.

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@bnoordhuis bnoordhuis changed the title src: make InternalModuleReadJSON great again src: make InternalModuleReadJSON linear again Jan 14, 2020
@bnoordhuis
src: make InternalModuleReadJSON() linear again
da6b66a 
Commits dcb6929, 4396beb and 8a96d05 turned the O(n) scan in
InternalModuleReadJSON() into an O(4n) scan. Fix the performance
regression by turning that into a linear scan again.
@bnoordhuis
bnoordhuis force-pushed the fix31340 branch from e8ed86b to da6b66a Compare January 14, 2020 10:49
@bnoordhuis
bnoordhuis dismissed ryanmurakami’s stale review January 14, 2020 10:49

obsolete

@bnoordhuis

bnoordhuis commented Jan 14, 2020

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not a wordplay on a right-wing slogan before or during merging.

A play on a left-wing slogan would've been okay then? I've changed it to something more boring, PTAL.
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@Trott

Trott commented Jan 15, 2020 •
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not a wordplay on a right-wing slogan before or during merging.

A play on a left-wing slogan would've been okay then?

The phrase is one that provokes strong reactions. I think it is reasonable to request that it be changed in a situation like this where using the phrase is unnecessary.

But yes, the fact that the slogan is right-wing is not really the problem, per se. Had it been a play on "Read my lips: no new taxes", I don't think it would generate the same reaction.

FWIW, I can definitely think of a few left-wing slogans that would be problematic.

I've changed it to something more boring, PTAL.

Let's make it even more boring and remove all vestiges of the wordplay. src: fix performance regression in node_file.cc or maybe src: fix performance regression in InternalModuleReadJSON?
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Trott
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LGTM with updated commit message

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nodejs-github-bot commented Jan 15, 2020

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CI: https://ci.nodejs.org/job/node-test-pull-request/28447/
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Trott pushed a commit that referenced this pull request Jan 15, 2020
@bnoordhuis @Trott
src: fix performance regression in node_file.cc
6623481 
Commits dcb6929, 4396beb and 8a96d05 turned the O(n) scan in
InternalModuleReadJSON() into an O(4n) scan. Fix the performance
regression by turning that into a linear scan again.

PR-URL: #31343
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Guy Bedford <[email protected]>
Reviewed-By: David Carlier <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Jan Krems <[email protected]>
@Trott

Trott commented Jan 15, 2020

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Landed in 6623481.

I updated the commit message on landing.
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@Trott Trott closed this Jan 15, 2020
@ljharb ljharb mentioned this pull request Jan 15, 2020
src: fix performance regression in node_file.cc #31340
Closed
@ljharb ljharb changed the title src: make InternalModuleReadJSON linear again src: fix performance regression in node_file.cc Jan 15, 2020
MylesBorins pushed a commit that referenced this pull request Jan 16, 2020
@bnoordhuis @MylesBorins
src: fix performance regression in node_file.cc
83f7b5a 
Commits dcb6929, 4396beb and 8a96d05 turned the O(n) scan in
InternalModuleReadJSON() into an O(4n) scan. Fix the performance
regression by turning that into a linear scan again.

PR-URL: #31343
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Guy Bedford <[email protected]>
Reviewed-By: David Carlier <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Jan Krems <[email protected]>
@codebytere codebytere mentioned this pull request Jan 16, 2020
v13.7.0 proposal #31382
Merged
codebytere pushed a commit that referenced this pull request Mar 14, 2020
@bnoordhuis @codebytere
src: fix performance regression in node_file.cc
23a5339 
Commits dcb6929, 4396beb and 8a96d05 turned the O(n) scan in
InternalModuleReadJSON() into an O(4n) scan. Fix the performance
regression by turning that into a linear scan again.

PR-URL: #31343
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Guy Bedford <[email protected]>
Reviewed-By: David Carlier <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Jan Krems <[email protected]>
codebytere pushed a commit that referenced this pull request Mar 17, 2020
@bnoordhuis @codebytere
src: fix performance regression in node_file.cc
a2f1825 
Commits dcb6929, 4396beb and 8a96d05 turned the O(n) scan in
InternalModuleReadJSON() into an O(4n) scan. Fix the performance
regression by turning that into a linear scan again.

PR-URL: #31343
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Guy Bedford <[email protected]>
Reviewed-By: David Carlier <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Jan Krems <[email protected]>
@codebytere codebytere mentioned this pull request Mar 17, 2020
v12.16.2 proposal #32313
Merged
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@hybrist hybrist hybrist approved these changes
@guybedford guybedford guybedford approved these changes
@Trott Trott Trott approved these changes
@addaleax addaleax addaleax approved these changes
@cjihrig cjihrig cjihrig approved these changes
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@devsnek devsnek devsnek left review comments
@devnexen devnexen devnexen approved these changes
@ryanmurakami ryanmurakami ryanmurakami left review comments
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@bnoordhuis @nodejs-github-bot @Trott @hybrist @guybedford @ryanmurakami @addaleax @cjihrig @devnexen @devsnek
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