stream: amortize writable buffer compaction

[gurgunday]

Context

Writable compacts its pending-write array after consuming more than 256 entries, even when most of the queue remains. Therefore draining a large backlog repeatedly shifts the remaining entries

Solution

Compact only once at least half the array has been consumed, keeping queue compaction amortized linear. Consumed entries are still cleared immediately

                                                      confidence   improvement   accuracy (*)    (**)   (***)
streams/writable-buffered-drain.js n=100 count=1024                  +11.54 %   ±20.95%  ±31.61%  ±50.44%
streams/writable-buffered-drain.js n=100 count=16384  ***            +13.38 %   ±1.93%  ±2.75%  ±4.00%
streams/writable-buffered-drain.js n=100 count=65536  ***           +107.78 %   ±5.53%  ±7.93%  ±11.62%

[nodejs-github-bot]

Review requested:

• @nodejs/performance
• @nodejs/streams

[mcollina]

lgtm

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.18%. Comparing base (b265340) to head (6c70f6e).
⚠️ Report is 26 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/streams/writable.js	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main   #65847    +/-   ##
========================================
  Coverage   90.18%   90.18%            
========================================
  Files         770      771     +1     
  Lines      264410   264622   +212     
  Branches    50230    50232     +2     
========================================
+ Hits       238449   238653   +204     
+ Misses      16966    16956    -10     
- Partials     8995     9013    +18     

Files with missing lines	Coverage Δ
lib/internal/streams/writable.js	96.30% <0.00%> (ø)

... and 36 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/77083/