From lsc1943 at gmail.com Tue Aug 5 01:59:43 2025 From: lsc1943 at gmail.com (Jack Ling) Date: Tue, 5 Aug 2025 09:59:43 +0800 Subject: JDK21/24 ZGC Generational Extra Performance Overhead Message-ID: Hello ZGC team, Recently we planned to upgrade JDK Our application is a Netty based gateway to route HTTP requests from ALB to upstream application servers. During the performance tests, we observed if using ZGC generational, it will cause extra 10% CPU overhead and the overall capacity was decreased 10% -15% which was a huge degradation. Unfortunately the normal ZGC was disabled in JDK 24. Attached JDK 21 and JDK 24 gc logs under the same workload, we could observe much more concurrent time cost when using ZGC generational. Would you help to advise what's the cause for the extra overhead using ZGC generational and how to optimize, thank you! -- Best Regards! Jack Ling -------------- next part -------------- An HTML attachment was scrubbed... URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: gclogs.zip Type: application/zip Size: 533748 bytes Desc: not available URL: From evaristojosec at yahoo.es Thu Aug 14 12:39:36 2025 From: evaristojosec at yahoo.es (=?UTF-8?Q?Evaristo_Jos=C3=A9_Camarero?=) Date: Thu, 14 Aug 2025 12:39:36 +0000 (UTC) Subject: Better understanding of Gen-ZGC promotion algorithm References: <305351824.4227898.1755175176145.ref@mail.yahoo.com> Message-ID: <305351824.4227898.1755175176145@mail.yahoo.com> Hi there, I would appreciate some high-level details about how Gen-ZGCis promoting objects from Young to Old. I can observe in the logs that tenuringthreshold is computed in runtime for every young collection, BUT I am NOT ableto fully understand the strategy. It looks to me that when allocation rate is higher thetenuring threshold is decreased and objects promotion happens faster (Bothbecause tenuring threshold is lower and because there are more frequent GCcycles). Is that correct? In our logs we observe the tenuring thresholdfluctuating between 1 and 12 (and then Young has Eden + N survivor areas). Myfeeling is that in some situations, object promotion could be a bit aggressiveand reclaiming the memory in the Old Generation will take a while. Is there any way to influence the promotion algorithm (e.g.guarantee a minimum of GC cycles)? I fully understand the ZGC strategy to avoidtoo much tuning and I agree that strategy is correct, BUT I ask the questionjust in case (I did NOT find anything in the WIKI, JEP or articles,presentations). A side effect in our case is that we monitor Old Generationsize to take some decisions (e.g. protect new data is provision in theDB...)? and in some cases, our system is overreacting. Thanks in advance, Evaristo ? -------------- next part -------------- An HTML attachment was scrubbed... URL: From stefan.karlsson at oracle.com Fri Aug 22 09:44:59 2025 From: stefan.karlsson at oracle.com (Stefan Karlsson) Date: Fri, 22 Aug 2025 11:44:59 +0200 Subject: CFV: New ZGC Reviewer: Axel Boldt-Christmas Message-ID: <50cc8eea-0d88-43d5-a7ea-87c2eeaa595e@oracle.com> I hereby nominate Axel Boldt-Christmas to ZGC Reviewer. Axel has made significant contributions to ZGC for three years now and is a major reviewer of changes related to ZGC. Votes are due by 2025-09-05T11:43+02:00. Only current ZGC Reviewers [1] are eligible to vote on this nomination.? Votes must be cast in the open by replying to this mailing list. For Three-Vote Consensus voting instructions, see [2]. Stefan Karlsson [1] https://openjdk.org/census [2] https://openjdk.org/projects/#reviewer-vote From stefan.karlsson at oracle.com Fri Aug 22 09:52:48 2025 From: stefan.karlsson at oracle.com (Stefan Karlsson) Date: Fri, 22 Aug 2025 11:52:48 +0200 Subject: CFV: New ZGC Committer: Stefan Johansson Message-ID: I hereby nominate Stefan Johansson to ZGC Committer. Stefan Johansson has lately been making significant changes to ZGC [3] Votes are due by 2025-09-05T11:48+02:00. Only current ZGC Committers [1] are eligible to vote on this nomination.? Votes must be cast in the open by replying to this mailing list. For Lazy Consensus voting instructions, see [2]. Stefan Karlsson [1] https://openjdk.org/census [2] https://openjdk.org/projects/#committer-vote [3] https://github.com/openjdk/jdk/commits?author=kstefanj From stefan.karlsson at oracle.com Fri Aug 22 09:53:06 2025 From: stefan.karlsson at oracle.com (Stefan Karlsson) Date: Fri, 22 Aug 2025 11:53:06 +0200 Subject: CFV: New ZGC Reviewer: Axel Boldt-Christmas In-Reply-To: <50cc8eea-0d88-43d5-a7ea-87c2eeaa595e@oracle.com> References: <50cc8eea-0d88-43d5-a7ea-87c2eeaa595e@oracle.com> Message-ID: <8a6d567f-24a3-428a-bc0a-bfafa9a41651@oracle.com> Vote: yes StefanK On 2025-08-22 11:44, Stefan Karlsson wrote: > I hereby nominate Axel Boldt-Christmas to ZGC Reviewer. > > Axel has made significant contributions to ZGC for three years now and > is a major reviewer of changes related to ZGC. > > Votes are due by 2025-09-05T11:43+02:00. > > Only current ZGC Reviewers [1] are eligible to vote > on this nomination.? Votes must be cast in the open by replying > to this mailing list. > > For Three-Vote Consensus voting instructions, see [2]. > > Stefan Karlsson > > [1] https://openjdk.org/census > [2] https://openjdk.org/projects/#reviewer-vote From stefan.karlsson at oracle.com Fri Aug 22 09:57:38 2025 From: stefan.karlsson at oracle.com (Stefan Karlsson) Date: Fri, 22 Aug 2025 11:57:38 +0200 Subject: CFV: New ZGC Committer: Stefan Johansson In-Reply-To: References: Message-ID: Vote: yes StefanK On 2025-08-22 11:52, Stefan Karlsson wrote: > I hereby nominate Stefan Johansson to ZGC Committer. > > Stefan Johansson has lately been making significant changes to ZGC [3] > > Votes are due by 2025-09-05T11:48+02:00. > > Only current ZGC Committers [1] are eligible to vote > on this nomination.? Votes must be cast in the open by replying > to this mailing list. > > For Lazy Consensus voting instructions, see [2]. > > Stefan Karlsson > > [1] https://openjdk.org/census > [2] https://openjdk.org/projects/#committer-vote > [3] https://github.com/openjdk/jdk/commits?author=kstefanj From erik.osterlund at oracle.com Fri Aug 22 10:01:03 2025 From: erik.osterlund at oracle.com (Erik Osterlund) Date: Fri, 22 Aug 2025 10:01:03 +0000 Subject: CFV: New ZGC Committer: Stefan Johansson In-Reply-To: References: Message-ID: <9A888419-5B25-4B70-AC31-F7466F0B2CED@oracle.com> Vote: yes /Erik > On 22 Aug 2025, at 11:53, Stefan Karlsson wrote: > > ?I hereby nominate Stefan Johansson to ZGC Committer. > > Stefan Johansson has lately been making significant changes to ZGC [3] > > Votes are due by 2025-09-05T11:48+02:00. > > Only current ZGC Committers [1] are eligible to vote > on this nomination. Votes must be cast in the open by replying > to this mailing list. > > For Lazy Consensus voting instructions, see [2]. > > Stefan Karlsson > > [1] https://openjdk.org/census > [2] https://openjdk.org/projects/#committer-vote > [3] https://github.com/openjdk/jdk/commits?author=kstefanj From erik.osterlund at oracle.com Fri Aug 22 10:01:36 2025 From: erik.osterlund at oracle.com (Erik Osterlund) Date: Fri, 22 Aug 2025 10:01:36 +0000 Subject: CFV: New ZGC Reviewer: Axel Boldt-Christmas In-Reply-To: <50cc8eea-0d88-43d5-a7ea-87c2eeaa595e@oracle.com> References: <50cc8eea-0d88-43d5-a7ea-87c2eeaa595e@oracle.com> Message-ID: <6AD3662D-E1BF-4433-9880-C1CE9B46ADCD@oracle.com> Vote: yes /Erik > On 22 Aug 2025, at 11:45, Stefan Karlsson wrote: > > ?I hereby nominate Axel Boldt-Christmas to ZGC Reviewer. > > Axel has made significant contributions to ZGC for three years now and is a major reviewer of changes related to ZGC. > > Votes are due by 2025-09-05T11:43+02:00. > > Only current ZGC Reviewers [1] are eligible to vote > on this nomination. Votes must be cast in the open by replying > to this mailing list. > > For Three-Vote Consensus voting instructions, see [2]. > > Stefan Karlsson > > [1] https://openjdk.org/census > [2] https://openjdk.org/projects/#reviewer-vote From joel.sikstrom at oracle.com Fri Aug 22 10:03:32 2025 From: joel.sikstrom at oracle.com (Joel Sikstrom) Date: Fri, 22 Aug 2025 10:03:32 +0000 Subject: CFV: New ZGC Committer: Stefan Johansson In-Reply-To: References: Message-ID: Vote: yes Joel Sikstr?m From: zgc-dev on behalf of Stefan Karlsson Date: Friday, 22 August 2025 at 11:53 To: zgc-dev at openjdk.org Subject: CFV: New ZGC Committer: Stefan Johansson I hereby nominate Stefan Johansson to ZGC Committer. Stefan Johansson has lately been making significant changes to ZGC [3] Votes are due by 2025-09-05T11:48+02:00. Only current ZGC Committers [1] are eligible to vote on this nomination. Votes must be cast in the open by replying to this mailing list. For Lazy Consensus voting instructions, see [2]. Stefan Karlsson [1] https://openjdk.org/census [2] https://openjdk.org/projects/#committer-vote [3] https://github.com/openjdk/jdk/commits?author=kstefanj -------------- next part -------------- An HTML attachment was scrubbed... URL: From rehn at rivosinc.com Fri Aug 22 11:01:21 2025 From: rehn at rivosinc.com (Robbin Ehn) Date: Fri, 22 Aug 2025 13:01:21 +0200 Subject: CFV: New ZGC Committer: Stefan Johansson In-Reply-To: References: Message-ID: Vote: yes On Fri, Aug 22, 2025 at 11:54?AM Stefan Karlsson wrote: > > I hereby nominate Stefan Johansson to ZGC Committer. > > Stefan Johansson has lately been making significant changes to ZGC [3] > > Votes are due by 2025-09-05T11:48+02:00. > > Only current ZGC Committers [1] are eligible to vote > on this nomination. Votes must be cast in the open by replying > to this mailing list. > > For Lazy Consensus voting instructions, see [2]. > > Stefan Karlsson > > [1] https://openjdk.org/census > [2] https://openjdk.org/projects/#committer-vote > [3] https://github.com/openjdk/jdk/commits?author=kstefanj