Feature #19437: Add marking and sweeping time to GC.stat

• Status: Closed
• Assignee: -
• Target version: -

[peterzhu2118 (Peter Zhu)]

Pull Request: https://github.com/ruby/ruby/pull/7304

There is a time key in GC.stat that gives us the total time spent in GC. However, we don't know what proportion of the time is spent between marking and sweeping. This makes it difficult to tune the GC as we're not sure where to focus our efforts on.

This PR adds keys marking_time and sweeping_time to GC.stat for the time spent marking and sweeping, in milliseconds.

[rubyFeedback (robert heiler)]

\o/

[AMomchilov (Alexander Momchilov)]

Hey Robert, I appreciate your excitement, but could you please refrain from commenting unless it's meaningfully contributing to the discussion?

You can show your support for this issue by clicking "like" in the top right corner ⬈

[peterzhu2118 (Peter Zhu)]

• Status changed from Open to Closed

Applied in changeset git|93ac7405b80cc61930d73da04441fa09af1851e1.

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Add marking and sweeping time to GC.stat

There is a time key in GC.stat that gives us the total time spent in
GC. However, we don't know what proportion of the time is spent between
marking and sweeping. This makes it difficult to tune the GC as we're
not sure where to focus our efforts on.

This PR adds keys marking_time and sweeping_time to GC.stat for the
time spent marking and sweeping, in milliseconds.

[Feature #19437]

[rubyFeedback (robert heiler)]

You can show your support for this issue by clicking "like" in the top right corner

Aha - I did not notice that before.

could you please refrain from commenting unless it's meaningfully contributing
to the discussion?

This is a situational question, though, as to what is to be considered "meaningful".
Ultimately it taps into being able to provide feedback about feature set xyz, or
not being able to provide feedback.

But, before this is misunderstood: I do not mind using the "Like" part for short
feedback.

[mame (Yusuke Endoh)]

Just a curious question. Is compaction time classified as marking_time or sweeping_time?

[ko1 (Koichi Sasada)]

Similar question with mame-san's #5, but at the last marking starts sweeping. does the current patch (already merged) split it?

[peterzhu2118 (Peter Zhu)]

Is compaction time classified as marking_time or sweeping_time?

It will be part of sweeping_time. I think it's not very accurate to have a compacting_time because we do sweeping during compaction, so I chose to put compaction time in sweeping_time. It might make sense to have compacting_time in the future, but since it's disabled by default and I'm not aware of any production services using auto-compaction in production (we only run GC.compact before forking here at Shopify), so we don't need this data right now.

does the current patch (already merged) split it?

I refactored the code so that the marking and sweeping phases are separated (in d7c1ca4.