Move desktop builds to ThinLTO #196308

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1. gaaclarke

   added

   team-engineOwned by Engine teamOwned by Engine team

   on Nov 10, 2026
2. gaaclarke commented on Nov 10, 2026

   

   gaaclarke

   on Nov 10, 2026

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   Skia is reporting real differences in text performance with LTO versus none, like 10% faster benchmarks.
3. gaaclarke commented on Nov 10, 2026

   

   gaaclarke

   on Nov 10, 2026

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   I implemented this locally and compared the build times and build sizes:

   	--no-lto	--thin-lto	Δ
   Clean build (wall)	142.7 s	151.9 s	+9.2 s (+6%)
   Link step alone	1.2 s	11.2 s	~10×
   Incremental rebuild	1.8 s	13.6 s	~7×
   libflutter_linux_gtk.so size	17.0 MB	18.2 MB	+6.8%

   So it increased size, we'd have to see some benefit of benchmarks.
4. gaaclarke commented on Nov 10, 2026

   

   gaaclarke

   on Nov 10, 2026

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   I ran txt_benchmarks with and without lto and on average it's 13% faster.

   Benchmark	no-LTO	ThinLTO	ThinLTO/no-LTO	p
   SkParagraphFixture/ShortLayout	1120 ns	942.8 ns	0.842	6.3e-08
   SkParagraphFixture/LongLayout	25.43 µs	20.39 µs	0.802	6.3e-08
   SkParagraphFixture/JustifyLayout	48.82 µs	42.99 µs	0.881	6.3e-08
   SkParagraphFixture/ManyStylesLayout	187.4 µs	153.6 µs	0.820	6.3e-08
   SkParagraphFixture/TextBigO/64	2295 ns	1894 ns	0.825	6.3e-08
   SkParagraphFixture/TextBigO/256	6853 ns	5571 ns	0.813	6.3e-08
   SkParagraphFixture/TextBigO/1024	42.65 µs	37.26 µs	0.874	6.3e-08
   SkParagraphFixture/TextBigO/4096	228.1 µs	205.8 µs	0.902	6.3e-08
   SkParagraphFixture/TextBigO/16384	1074 µs	963.1 µs	0.896	6.3e-08
   SkParagraphFixture/StylesBigO/8	381.7 µs	330.6 µs	0.866	6.3e-08
   SkParagraphFixture/StylesBigO/16	378.6 µs	328.4 µs	0.867	6.3e-08
   SkParagraphFixture/StylesBigO/64	379.3 µs	329.6 µs	0.869	6.3e-08
   SkParagraphFixture/StylesBigO/256	380.1 µs	327.6 µs	0.862	6.3e-08
   SkParagraphFixture/StylesBigO/1024	382.9 µs	329.0 µs	0.859	6.3e-08
   SkParagraphFixture/StylesBigO/4096	381.1 µs	329.5 µs	0.865	6.3e-08
   SkParagraphFixture/PaintSimple	12.99 µs	12.74 µs	0.980	3.9e-05
   SkParagraphFixture/PaintLarge	314.6 µs	307.8 µs	0.978	3.2e-07
   SkParagraphFixture/PaintDecoration	830.1 µs	801.4 µs	0.965	6.3e-08
   SkParagraphFixture/SimpleBuilder	809.6 ns	657.0 ns	0.811	6.3e-08
5. gaaclarke commented on Nov 11, 2026

   

   gaaclarke

   on Nov 11, 2026

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   Rusino has good suggestions on tweaking thinlto: #196314 (comment)
6. woprandi

   added a commit that references this issue on Nov 11, 2026

   Moves linux to ThinLTO. (flutter#196314)

   ...

   f9d2a0a