934946 - Add most-recently-used-contentlists cache

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Olli Pettay [:smaug][[e-mail]]]

Attachment: patch

Looks like adding a simple most-recently-used-contentlists cache helps
about 20% with Bug 916851, and it also speeds up dromaeo dom-query.

Somewhat dirty approach. In theory a hashtable should just do its job fast enough, though
this kind of cache let's one to inline more I guess.
I tried few sizes and 31 seemed to give quite stable results without being too huge.

https://tbpl.mozilla.org/?tree=Try&rev=be36926b326b

I tried adding also 3rd level of cache, by caching the most recently used list.
That helped even more with dromaeo dom-query, but was worse with Bug 916851 -
as expected.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Attachment: Sketch of alternate approach using js::HashSet

So I tried this, and it's faster than what we have now, but not as fast as having 31-element cache.  In fact, it about splits the difference between that 31-element cache and now.

Comment 2

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 827338 [details] [diff] [review]
patch

Could we wrap up the cache in a struct with at least a method to compute the right index?

>+  uint32_t mHash;

const uint32_t.

r=me with that, since I have no better ideas.  :(

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Not sure about the struct, but a helper method would be nice indeed.

Comment 4

[Olli Pettay [:smaug][[e-mail]]]

Attachment: const mHash, helper method for index

Comment 5

[Olli Pettay [:smaug][[e-mail]]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/5ee306a9908d

Comment 6

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/5ee306a9908d