May 2023 - zgc-dev - openjdk.org

RFR: 8306656: Fix age table logging
by Erik Helin 02 Jan '24

02 Jan '24

Hey all, please review this patch that updates the age table logging. The logging now looks like: [1.946s][info][gc,reloc ] GC(22) y: Age Table: [1.946s][info][gc,reloc ] GC(22) y: Live Small Medium Large [1.946s][info][gc,reloc ] GC(22) y: Eden 0M -> 0M 300 -> 300 0 -> 0 0 -> 0 [1.946s][info][gc,reloc ] GC(22) y: Survivor 1 0M -> 0M 2 -> 2 0 -> 0 0 -> 0 [1.946s][info][gc,reloc ] GC(22) y: Survivor 2 0M -> 0M 1 -> 0 0 -> 0 0 -> 0 [1.946s][info][gc,reloc ] GC(22) y: Survivor 3 0M -> 0M 1 -> 1 0 -> 0 0 -> 0 [1.946s][info][gc,reloc ] GC(22) y: Survivor 4 0M -> 0M 0 -> 1 0 -> 0 0 -> 0 The first column is the size of the live objects with the given age and how that has changed since the previous collection. The remaining columns are the number of pages of the given age and how those have changed from the previous collection to the current one (so the format is `<previous> -> <current>`). This makes it easy to spot a change in behavior in objects' lifetimes from one collection to another: if objects have similar lifetimes compared to the previous collection then the distribution of pages should be similar between the current collection and the previous collection. _Note_: I would like to make the table adapt to live sizes smaller than one megabyte, but that should probably be done for the logging as a whole, not just for the age table. I also cleaned up some minor stuff as I went along. Testing: - [x] Tier 1-3 (macOS-aarch64, Windows-x64, Linux-x64, Linux-aarch64) - [x] Local testing on macOS-aarch64 Thanks, Erik ------------- Commit messages: - Rework age table logging Changes: https://git.openjdk.org/zgc/pull/19/files Webrev: https://webrevs.openjdk.org/?repo=zgc&pr=19&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8306656 Stats: 200 lines in 10 files changed: 104 ins; 52 del; 44 mod Patch: https://git.openjdk.org/zgc/pull/19.diff Fetch: git fetch https://git.openjdk.org/zgc.git pull/19/head:pull/19 PR: https://git.openjdk.org/zgc/pull/19

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Help Fix Broken Links on ZGC Wiki Page
by Hao Tang 25 May '23

25 May '23

Hi there! I noticed that some of the hyperlinks (e.g., ZGC technical slides) on ZGC Wiki page (https://wiki.openjdk.org/display/zgc <https://wiki.openjdk.org/display/zgc >) are not working anymore. I've found these slides to be really helpful in the past, so I was wondering if it would be possible to update those links and make them available again. Thanks very much for your help! Best regards, Hao Tang

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ZGC and 1G pages?
by Thomas Stüfe 08 May '23

08 May '23

Hi, ZGC, on Linux, seems only compatible with 2M pages. Seeing that ZGC is often used with very large heaps, is support for 1GB pages planned? Especially if one disregards uncommitting (-ZUncommit), 1G pages could be a speed boost for customers with gigantic heaps, as well as reduce their number of VMAs. Thanks, Thomas

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