| <!DOCTYPE html> |
| <body> |
| <pre id="log"></pre> |
| <script src="../resources/runner.js"></script> |
| <script src="resources/declarative.js"></script> |
| <script> |
| |
| /* |
| This test tries to measure the overhead associated with parsing and |
| attaching one shadow root to the tree, as compared to an "ordinary" |
| element. To measure this, we make three timing measurements: |
| |
| t1 = A + (b + d)x |
| t2 = A + (c + d)x |
| t3 = A + (2b + d)x |
| |
| where: |
| A = fixed overhead associated with parsing and tree building |
| b = per light-dom "ordinary" node time |
| c = per shadow root time |
| d = per "other element" node time. This is the other elements, e.g. <span> |
| and <!-- comment --> nodes, mixed in with the test markup. To solve |
| for the percent overhead, we need this to be non-zero (see below). |
| x = number of repeats of the test block, per run of the test. |
| |
| we want to solve for: |
| (c/b - 1) = percent overhead, per shadow root |
| |
| So: |
| (t2 - t1)/x = c - b = (c/b - 1)b |
| (t3 - t1)/x = b |
| (c/b - 1) = (t2-t1)/(t3-t1) = percent overhead |
| */ |
| |
| const depth = 6; |
| const copies = 100; |
| const shadowHtml = getShadowMarkup(true, depth, copies); |
| const lightDomHtml1 = getShadowMarkup(false, depth, copies, /*lightDomDuplicates=*/1); |
| const lightDomHtml2 = getShadowMarkup(false, depth, copies, /*lightDomDuplicates=*/2); |
| |
| PerfTestRunner.measureValue({ |
| description: 'This benchmark tests the overhead of declarative Shadow DOM', |
| unit: 'percent', |
| run: function() { |
| let total_overhead = 0; |
| let total_samples = 0; |
| for (let i = 0; i < 100; i++) { |
| const t1 = measureParse(lightDomHtml1); |
| const t2 = measureParse(shadowHtml); |
| const t3 = measureParse(lightDomHtml2); |
| if (t2 > t1 && t3 > t1) { |
| total_overhead += (t2-t1) / (t3-t1); |
| ++total_samples; |
| } |
| } |
| PerfTestRunner.assert_true(total_samples>3,'Too many skipped measurements'); |
| // The result is the total overhead, in *percent*, *per shadow root*. |
| return 100*total_overhead/total_samples; |
| } |
| }); |
| </script> |
