Auto merge of #17198 - bzbarsky:bigger-sharing-cache, r=bholley

Increase the size of the style sharing cache to 31.

Still a lot of guesswork here, but this does seem to get us better sharing.  See
https://bugzilla.mozilla.org/show_bug.cgi?id=1369621 for some data.

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- [X] These changes fix https://bugzilla.mozilla.org/show_bug.cgi?id=1369621

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This commit is contained in:
bors-servo 2017-06-07 04:13:50 -07:00 committed by GitHub
commit fdd1d719f3
2 changed files with 10 additions and 6 deletions

View file

@ -37,9 +37,11 @@ use traversal::{DomTraversal, PerLevelTraversalData, PreTraverseToken};
///
/// Larger values will increase style sharing cache hits and general DOM locality
/// at the expense of decreased opportunities for parallelism. The style sharing
/// cache can hold 8 entries, but not all styles are shareable, so we set this
/// value to 16. These values have not been measured and could potentially be
/// tuned.
/// cache can hold 31 entries, but not all styles are shareable, so we set this
/// value to 16. The size of the cache has been measured to provide pretty good
/// sharing on a few pages, but could probably use more measurement and tuning.
/// The work unit size is a bit of a guess at the moment; again could use
/// measurement and tuning.
pub const WORK_UNIT_MAX: usize = 16;
/// Verify that the style sharing cache size doesn't change. If it does, we should
@ -48,7 +50,7 @@ pub const WORK_UNIT_MAX: usize = 16;
/// have surprising effects on the parallelism characteristics of the style system.
#[allow(dead_code)]
fn static_assert() {
unsafe { mem::transmute::<_, [u32; STYLE_SHARING_CANDIDATE_CACHE_SIZE]>([1; 8]); }
unsafe { mem::transmute::<_, [u32; STYLE_SHARING_CANDIDATE_CACHE_SIZE]>([1; 31]); }
}
/// A list of node pointers.

View file

@ -84,8 +84,10 @@ use stylist::{ApplicableDeclarationBlock, Stylist};
mod checks;
/// The amount of nodes that the style sharing candidate cache should hold at
/// most.
pub const STYLE_SHARING_CANDIDATE_CACHE_SIZE: usize = 8;
/// most. We'd somewhat like 32, but ArrayDeque only implements certain backing
/// store sizes. A cache size of 32 would mean a backing store of 33, but
/// that's not an implemented size: we can do 32 or 40.
pub const STYLE_SHARING_CANDIDATE_CACHE_SIZE: usize = 31;
/// Controls whether the style sharing cache is used.
#[derive(Clone, Copy, PartialEq)]