Bugzilla

In [bug 1879143](https://bugzilla.mozilla.org/show_bug.cgi?id=1879143), the per-zone atom cache was switched to use AtomCacheHashTable. Further investigations, including from the regression reported in [bug 1888676](https://bugzilla.mozilla.org/show_bug.cgi?id=1888676), have shown the further improvements are possible by making this cache be associative.

SP3 results are pretty positive with this change: [2k cache w/ 2-way associativity](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=0f21b7054a06b4599391790d99117c5a3b5e970d&originalSignature=4586009&newSignature=4586009&framework=13&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1), [2k cache w/ 2-way associativity](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=f80973bd29349b09e6dbc770197c39fdb3f6670b&originalSignature=4586009&newSignature=4586009&framework=13&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1), [2k cache with 4-way associativity](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=71e6ec76466ac6b2c0c2172af5ef8101e79cb3b7&originalSignature=4586009&newSignature=4586009&framework=13&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1).

DAMP results (which can be seen in those comparison results, for example [here](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=71e6ec76466ac6b2c0c2172af5ef8101e79cb3b7&originalSignature=4763280&newSignature=4763280&framework=12&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1)) are decidedly more mixed - some tests get significantly better with high confidence and some get significantly worse with high confidence. Further investigation on why this is is warranted.

In [bug 1879143](https://bugzilla.mozilla.org/show_bug.cgi?id=1879143), the per-zone atom cache was switched to use AtomCacheHashTable. Further investigations, including from the regression reported in [bug 1888676](https://bugzilla.mozilla.org/show_bug.cgi?id=1888676), have shown the further improvements are possible by making this cache be associative.

SP3 results are pretty positive with this change: [2k cache w/ 2-way associativity](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=0f21b7054a06b4599391790d99117c5a3b5e970d&originalSignature=4586009&newSignature=4586009&framework=13&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1), [2k cache w/ 2-way associativity](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=f80973bd29349b09e6dbc770197c39fdb3f6670b&originalSignature=4586009&newSignature=4586009&framework=13&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1), [2k cache with 4-way associativity](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=71e6ec76466ac6b2c0c2172af5ef8101e79cb3b7&originalSignature=4586009&newSignature=4586009&framework=13&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1).

DAMP results (which can be seen in those comparison results, for example [here](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=71e6ec76466ac6b2c0c2172af5ef8101e79cb3b7&originalSignature=4763280&newSignature=4763280&framework=12&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1)) are decidedly more mixed - some tests get significantly better with high confidence and some get significantly worse with high confidence. That some tests get so much worse with an associative test is unexpected so further investigation on why this is is warranted.

In [bug 1879143](https://bugzilla.mozilla.org/show_bug.cgi?id=1879143), the per-zone atom cache was switched to use AtomCacheHashTable. Further investigations, including from the regression reported in [bug 1888676](https://bugzilla.mozilla.org/show_bug.cgi?id=1888676), have shown the further improvements are possible by making this cache be associative.

SP3 results are pretty much universally positive with this change: [2k cache w/ 2-way associativity](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=0f21b7054a06b4599391790d99117c5a3b5e970d&originalSignature=4586009&newSignature=4586009&framework=13&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1), [2k cache w/ 2-way associativity](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=f80973bd29349b09e6dbc770197c39fdb3f6670b&originalSignature=4586009&newSignature=4586009&framework=13&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1), [2k cache with 4-way associativity](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=71e6ec76466ac6b2c0c2172af5ef8101e79cb3b7&originalSignature=4586009&newSignature=4586009&framework=13&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1).

DAMP results (which can be seen in those comparison results, for example [here](https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=71e6ec76466ac6b2c0c2172af5ef8101e79cb3b7&originalSignature=4763280&newSignature=4763280&framework=12&application=firefox&originalRevision=494499dbf98a5df49e9c69576e344df25059ee8e&page=1&replicates=1)) are decidedly more mixed - some tests get significantly better with high confidence and some get significantly worse with high confidence. That some tests get so much worse with an associative test is unexpected so further investigation on why this is is warranted.