On Tue, Jun 21, 2022 at 11:36 AM Jianxiao Lu <[email protected]> wrote:

> Thanks for the explanation. The second screenshot is 1520ms~1560ms in
> fact. The snapshots were taken from the first major gc running webtooling.
> Because I believe the first major gcs are relatively predictable and
> consistent. (Maybe I am wrong).
>
> I will check with your suggestion later. Does the gc-tracer already have
> something to record the mark-bytes/ms ? Or I need to try to implement one?
>

--trace-concurrent-marking will log concurrently marked bytes and timespans
which can be used to compute the speed. Any custom logging will also do
though.

-Michael


>
> Thanks,
> Jianxiao
>
> On Tuesday, June 21, 2022 at 3:08:10 PM UTC+8 [email protected]
> wrote:
>
>> On Tue, Jun 21, 2022 at 8:33 AM Jianxiao Lu <[email protected]> wrote:
>>
>>>
>>> https://source.chromium.org/chromium/chromium/src/+/main:v8/src/heap/concurrent-marking.h;l=59?q=kMaxTasks&sq=&ss=chromium
>>>
>>> The code comments above seems out of date. So I wonder if this
>>> limitation is intentional or just no be updated in time.
>>>
>>> Here is a snapshot in webtooling (d8).
>>>
>>> [image: 7.png]
>>>
>>> After I tuned the worker number(
>>> https://chromium-review.googlesource.com/c/v8/v8/+/3711496):
>>> [image: 15.png]
>>>
>>> Seems that we can benefit from more worker?
>>>
>>
>> This really depends on what the average size of the heap is.The numbers
>> were chosen as a compromise between small and large heaps and low-end vs
>> desktop devices. Also, the algorithm doesn't scale linearly but there's
>> smaller trade offs here and there which add up as the # tasks are increased.
>>
>> Did the absolute time actually improve? I see 1280ms-1340ms in the first
>> screenshot vs 1520ms-1580ms. You could check marked bytes/s as a proxy of
>> whether the helper tasks are still efficient or not.
>>
>> -Michael
>>
>>
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