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Backport 6893 for v6.x (buffer: improve creation performance) #7349

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Backport 6893 for v6.x (buffer: improve creation performance) #7349

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Checklist
  • make -j4 test (UNIX) or vcbuild test nosign (Windows) passes
  • the commit message follows commit guidelines
Affected core subsystem(s)

buffer

Description of change

This is a backport of #6893 for v6.x as per @evanlucas' request. Applied almost cleanly.

Improves performance of allocating unsafe buffers, creating buffers from
an existing ArrayBuffer and creating .slice(...) from existing Buffer by
avoiding deoptimizing change of prototype after Uint8Array allocation
in favor of ES6 native subclassing.

This is done through an internal ES6 class that extends Uint8Array and
is used for allocations, but the regular Buffer function is exposed, so
calling Buffer(...) with or without `new` continues to work as usual
and prototype chains are also preserved.

Performance wins for .slice are +120% (2.2x), and, consequently, for
unsafe allocations up to +95% (1.9x) for small buffers, and for safe
allocations (zero-filled) up to +30% (1.3x).

PR-URL: #6893
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Сковорода Никита Андреевич <[email protected]>
@nodejs-github-bot nodejs-github-bot added buffer Issues and PRs related to the buffer subsystem. c++ Issues and PRs that require attention from people who are familiar with C++. labels Jun 21, 2016
@thefourtheye
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cc @nodejs/buffer

@MylesBorins
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@trevnorris
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LGTM

@RReverser
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Merging today if no objections.

RReverser added a commit that referenced this pull request Jun 25, 2016
Improves performance of allocating unsafe buffers, creating buffers from
an existing ArrayBuffer and creating .slice(...) from existing Buffer by
avoiding deoptimizing change of prototype after Uint8Array allocation
in favor of ES6 native subclassing.

This is done through an internal ES6 class that extends Uint8Array and
is used for allocations, but the regular Buffer function is exposed, so
calling Buffer(...) with or without `new` continues to work as usual
and prototype chains are also preserved.

Performance wins for .slice are +120% (2.2x), and, consequently, for
unsafe allocations up to +95% (1.9x) for small buffers, and for safe
allocations (zero-filled) up to +30% (1.3x).

PR-URL: #7349
Ref: #6893
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Сковорода Никита Андреевич <[email protected]>
Reviewed-By: Trevor Norris <[email protected]>
@RReverser
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Landed in ac8e1bf

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5 participants