On 2/13/14 2:42 PM, Boris Zbarsky wrote:
Then you go through this list (this part should parallelize pretty
nicely, btw, except for the overflow area updates on parents) and reflow
them all, since now you know their containing block sizes, and you
update overflow areas. Again, if there are abs pos kids you add to a
list, etc.
I have a couple of concerns about this from a performance point of view.
1. This creates multiple sequential barriers, which can result in a
parallelism hazard. As an extreme case, consider:
<style>div { position: absolute; }</style>
<div><div><div><div><div>...
This will effectively result in fully sequential layout because you have
to wait until layout to finish to start working on the new absolutely
positioned kids you found, and so on.
2. The overhead of updating parents' overflow areas over and over again.
In fact a page like above will result in O(n^2) updates of parents'
overflow areas where n is the number of nodes, unless I'm missing something.
Can we tweak the algorithm in some way to avoid these hazards?
Patrick
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