which flags should I pass to V8?

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Chunhui Li

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Jun 26, 2019, 11:32:54 PM6/26/19
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 I'm using embedded v8 in my server. Each isolate will be about 40M, and there will be 100 isolates at the same time. What should I pass to V8 with --max-semi-space-size and/or --max-old-space-size?

Yang Guo

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Jun 27, 2019, 3:40:34 AM6/27/19
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Adding the right folks. 

On Thu, Jun 27, 2019, 05:32 Chunhui Li <lichun...@bytedance.com> wrote:
 I'm using embedded v8 in my server. Each isolate will be about 40M, and there will be 100 isolates at the same time. What should I pass to V8 with --max-semi-space-size and/or --max-old-space-size?

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Chunhui Li

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Jun 27, 2019, 3:47:03 AM6/27/19
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Adding one another condition, as time goes on, some of the isolates will be disposed and some other new isolates will be created. 

Jakob Kummerow

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Jun 27, 2019, 6:08:36 AM6/27/19
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The first thing to try is always not to pass any special flags. Does that run into any issues?

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Ulan Degenbaev

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Jun 27, 2019, 6:21:31 AM6/27/19
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--max-semi-space-size=1 --max-old-space-size=37 would keep the heap size at around 40.

FYI, I am adding a new flag --max-heap-size that will be available in future versions of V8: https://chromium-review.googlesource.com/c/v8/v8/+/1679500

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Ulan Degenbaev

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Jun 27, 2019, 6:27:30 AM6/27/19
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Clarification: if 40MB is the expected size of live objects, then you probably want to have some free space in heap to avoid GC storm.
So --max-semi-space-size=1 --max-old-space-size=80 might be better in that case.

Chunhui Li

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Jun 27, 2019, 6:29:53 AM6/27/19
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My question is whether this setting is the limitation of one isolate? Or is it a global setting?

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Ulan Degenbaev

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Jun 27, 2019, 6:36:25 AM6/27/19
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The flag is per isolate

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Chunhui Li

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Jun 27, 2019, 10:51:55 AM6/27/19
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Why is it enough to set semi-space-size to 1?

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