Impromptu perf fix: NSString _fastestEncoding #1623
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ms-jihua
commented
Jan 4, 2017
| options:(NSStringEncodingConversionOptions)options | ||
| range:(NSRange)range | ||
| remainingRange:(NSRangePointer)left { | ||
| maxLength:(NSUInteger)maxBuf |
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looks like our clang-format got updated (10/31) since the last change to this file (early sep)
rajsesh
reviewed
Jan 4, 2017
| NSRange range; | ||
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| for (range.location = 0; range.location < length; range.location += range.length) { | ||
| UniChar buf[bufferSize]; |
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UniChar buf[bufferSize] [](start = 8, length = 23)
move this buffer outside the for loop.
rajsesh
reviewed
Jan 4, 2017
| for (int32_t i = 0; i < [self length]; i++) { | ||
| if ([self characterAtIndex:i] > 0x7F) { | ||
| // Check characters in chunks for perf reasons | ||
| const size_t bufferSize = 128; |
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128 [](start = 30, length = 3)
consider making this bigger (512?).
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Found while checking CTCatalog affine transform test. In cases of longer strings, _DWriteGetFrame() spends an inordinate amount of time in: _DWriteGetFrame (~30%) -> [NSString substring...] (~27%) -> [NSString _fastestEncodingWith...] (~25%) (sample trace) Changed this function to not call [self length] every iteration, fetch characters in chunks. After this change, the same test looks like: _DWriteGetFrame (~5%) -> [NSString substring...] (~1.2%) -> [NSString _fastestEncodingWith...] (~0.5%) (sample trace) Related to microsoft#1621
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Found while checking CTCatalog affine transform test.
In cases of longer strings, _DWriteGetFrame() spends an inordinate amount of time in:
_DWriteGetFrame (~30%) -> [NSString substring...] (~27%) -> [NSString _fastestEncodingWith...] (~25%) (sample trace)
Changed this function to not call [self length] every iteration, fetch characters in chunks.
After this change, the same test looks like:
_DWriteGetFrame (~5%) -> [NSString substring...] (~1.2%) -> [NSString _fastestEncodingWith...] (~0.5%) (sample trace)
This change is