1346065 - stylo: Expose STYLO_THREADS environment value and add an assertion in nsRefreshDriver::EnsureTimerStarted()

Status: NEW

(Core :: CSS Parsing and Computation, enhancement, P4)

Description

[Hiroyuki Ikezoe (:hiro)]

See bug 1341985 comment 41.

We well add an assertion in nsRefreshDriver::EnsureTimerStarted() in bug 1341985 that checks that we are not in the servo traversal or we are on the main-thread.  But if the STYLO_THREADS value is 1, the assertion is not useful, we do avoid the situation somehow.  But at this moment I don't want to use PR_GetEnv(XX) in nsRefreshDriver. Instead I'd prefer to add a function named StyloThreadsNum() or something somewhere.

Comment 1

[Cameron McCormack (:heycam)]

I don't think we should use the STYLO_THREADS environment variable directly, since it is only one way of determining how many style worker threads get created.  (If the variable is not set, we do num_cpus * 0.75 or something.)  Also there are plans to heuristically decide when to perform restyling sequentially (bug 1345691).

To do this I guess we need to expose something from the rust side.  But I don't think this is high priority.

Comment 2

[Brian Birtles (:birtles, Feb 26~ parental leave)]

P4 based on Cameron's assessment in comment 1.

Comment 3

[Chris Peterson [:cpeterson]]

status-firefox57=wontfix unless someone thinks this bug should block 57