530636 - Workers: Number of backing OS threads should be chosen dynamically based on HW concurrency

Status: RESOLVED WONTFIX

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

Description

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

A reasonable choice might be |concurrency-1| --- so e.g. a machine with 16 HW threads would have 15 OS threads allocated to the Worker pool.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Hmm...  We typically have at least two threads running already (UI thread and JS free() thread), no?

Comment 2

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Also necko, and the JS "watchdog" thread, IIRC.  But this bug only deals with the number of threads allocated to workers; if we're worried about degrading performance of other threads, we should perhaps allocate |concurrency - #expected often-running threads|.  I had "#expected often-running threads == 1" in comment 0, but you're right in pointing out that that may be too simplistic.  Probably need hard data to set this knob correctly.

Comment 3

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

(In reply to comment #2)
> Also necko, and the JS "watchdog" thread, IIRC.

And the HTML parser thread, soon, probably.

Comment 4

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Attachment: Choose number of threads allocated to workers based on hardware concurrency

Straightforward first cut.

Comment 5

[Ben Turner (not reading bugmail, use the needinfo flag!)]

We've opted to let each worker have its own thread now.