501186 - Profile object creation performance

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[David Mandelin [:dmandelin]]

Attachment: Test case

Results of attached test case:

               run time (ms)  empty loop run time (ms)      cycles/obj alloc
js -j (TM)         1307               38                        280
jsc (webkit)        497               32                         86
v8                  397              104                         65

We are 3.3-4.3x slower at allocating new empty objects. Let's find out why and fix it.

Comment 1

[Brendan Eich [:brendan]]

See bug 501189 comment 1 et seq.

/be

Comment 2

[Andreas Gal :gal]

Attachment: patch

I don't see any speedup from this. Maybe I am not measuring right though.

Comment 3

[Andreas Gal :gal]

Gregor, can you measure with this patch? If that moves the needle even a little, I can remove the other division too. I just want to make sure we are not chasing a ghost here.

Comment 4

[Gregor Wagner]

I dont have the 1:1 mapping from source code to the disassembled instructions.
There is still one division left where we spend now 50% of the time in this function due to shark. Probably its the GC_FREELIST_INDEX macro.