Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/23/18 11:04 PM, Mandy Chung wrote: On 10/23/18 10:34 PM, David Holmes wrote: On 24/10/2018 8:30 AM, dean.l...@oracle.com wrote: On 10/23/18 2:51 PM, David Holmes wrote: Hi Dean, On 24/10/2018 4:05 AM, dean.l...@oracle.com wrote: On 10/23/18 9:46 AM, dean.l...@oracle.com wrote: On

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/23/18 10:34 PM, David Holmes wrote: On 24/10/2018 8:30 AM, dean.l...@oracle.com wrote: On 10/23/18 2:51 PM, David Holmes wrote: Hi Dean, On 24/10/2018 4:05 AM, dean.l...@oracle.com wrote: On 10/23/18 9:46 AM, dean.l...@oracle.com wrote: On 10/22/18 3:31 PM, David Holmes wrote: Sorry

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 24/10/2018 8:30 AM, dean.l...@oracle.com wrote: On 10/23/18 2:51 PM, David Holmes wrote: Hi Dean, On 24/10/2018 4:05 AM, dean.l...@oracle.com wrote: On 10/23/18 9:46 AM, dean.l...@oracle.com wrote: On 10/22/18 3:31 PM, David Holmes wrote: Sorry Dean I'm concerned about a thread

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/23/18 3:30 PM, dean.l...@oracle.com wrote: On 10/23/18 2:51 PM, David Holmes wrote: OK, but even if the regular benchmarks don't show a difference, I'd feel better if microbenchmarks were not affected.  What if I go back to the original approach and add locking:    static jlong

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/23/18 2:51 PM, David Holmes wrote: Hi Dean, On 24/10/2018 4:05 AM, dean.l...@oracle.com wrote: On 10/23/18 9:46 AM, dean.l...@oracle.com wrote: On 10/22/18 3:31 PM, David Holmes wrote: Sorry Dean I'm concerned about a thread termination bottleneck with this. A simple microbenchmark

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

Hi Dean, On 24/10/2018 4:05 AM, dean.l...@oracle.com wrote: On 10/23/18 9:46 AM, dean.l...@oracle.com wrote: On 10/22/18 3:31 PM, David Holmes wrote: Sorry Dean I'm concerned about a thread termination bottleneck with this. A simple microbenchmark that creates 500,000 threads that have to

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/23/18 9:46 AM, dean.l...@oracle.com wrote: On 10/22/18 3:31 PM, David Holmes wrote: Sorry Dean I'm concerned about a thread termination bottleneck with this. A simple microbenchmark that creates 500,000 threads that have to run and terminate, shows a 15+% slowdown on my Linux box. I

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/22/18 3:31 PM, David Holmes wrote: Sorry Dean I'm concerned about a thread termination bottleneck with this. A simple microbenchmark that creates 500,000 threads that have to run and terminate, shows a 15+% slowdown on my Linux box. I tried to find some kind of real benchmarks that

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

Sorry Dean I'm concerned about a thread termination bottleneck with this. A simple microbenchmark that creates 500,000 threads that have to run and terminate, shows a 15+% slowdown on my Linux box. I tried to find some kind of real benchmarks that covers thread termination but couldn't see

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/18/18 6:12 PM, Mandy Chung wrote: On 10/18/18 12:27 AM, David Holmes wrote: Hi Dean, On 18/10/2018 2:06 PM, dean.l...@oracle.com wrote: You're right, I missed that.  I think the right thing to do is call current_thread_exiting while holding the Threads_lock. Then we can get rid of

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/18/18 12:27 AM, David Holmes wrote: Hi Dean, On 18/10/2018 2:06 PM, dean.l...@oracle.com wrote: You're right, I missed that.  I think the right thing to do is call current_thread_exiting while holding the Threads_lock. Then we can get rid of the parallel atomic counters.  So, here's

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

Hi Dean, On 18/10/2018 2:06 PM, dean.l...@oracle.com wrote: On 10/17/18 7:07 PM, David Holmes wrote: Hi Dean, This still seems racy to me. We increment all counts under the Threads_lock but we still decrement without the Threads_lock. So we can lose updates to the perfCounters.  117  

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/17/18 7:07 PM, David Holmes wrote: Hi Dean, This still seems racy to me. We increment all counts under the Threads_lock but we still decrement without the Threads_lock. So we can lose updates to the perfCounters.  117   _total_threads_count->inc();  118  

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

Thanks, Mandy! dl On 10/17/18 6:35 PM, Mandy Chung wrote: On 10/17/18 3:18 PM, dean.l...@oracle.com wrote: New webrevs, full and incremental: http://cr.openjdk.java.net/~dlong/8021335/webrev.6/ http://cr.openjdk.java.net/~dlong/8021335/webrev.6.diff/ I like it better without all the

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

Hi Dean, This still seems racy to me. We increment all counts under the Threads_lock but we still decrement without the Threads_lock. So we can lose updates to the perfCounters. 117 _total_threads_count->inc(); 118 Atomic::inc(&_atomic_threads_count); 119 int count =

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/17/18 3:18 PM, dean.l...@oracle.com wrote: New webrevs, full and incremental: http://cr.openjdk.java.net/~dlong/8021335/webrev.6/ http://cr.openjdk.java.net/~dlong/8021335/webrev.6.diff/ I like it better without all the asserts too. Looks good to me. Mandy

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

Thanks JC! dl On 10/17/18 5:06 PM, JC Beyler wrote: Hi Dean, The new webrev looks much better :) LGTM (not a reviewer though :-)). Thanks, Jc On Wed, Oct 17, 2018 at 3:19 PM > wrote: On 10/17/18 2:38 PM, Mandy Chung wrote: On 10/17/18 2:13 PM,

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/17/18 2:38 PM, Mandy Chung wrote: On 10/17/18 2:13 PM, dean.l...@oracle.com wrote: On 10/17/18 1:41 PM, Mandy Chung wrote: On 10/16/18 7:33 PM, David Holmes wrote: Hi Dean, Thanks for tackling this. I'm still struggling to fully grasp why we need both the PerfCounters and the

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/17/18 2:13 PM, dean.l...@oracle.com wrote: On 10/17/18 1:41 PM, Mandy Chung wrote: On 10/16/18 7:33 PM, David Holmes wrote: Hi Dean, Thanks for tackling this. I'm still struggling to fully grasp why we need both the PerfCounters and the regular counters. I get that we have to

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/17/18 1:41 PM, Mandy Chung wrote: On 10/16/18 7:33 PM, David Holmes wrote: Hi Dean, Thanks for tackling this. I'm still struggling to fully grasp why we need both the PerfCounters and the regular counters. I get that we have to decrement the live counts before ensure_join() has

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/16/18 7:33 PM, David Holmes wrote: Hi Dean, Thanks for tackling this. I'm still struggling to fully grasp why we need both the PerfCounters and the regular counters. I get that we have to decrement the live counts before ensure_join() has allowed Thread.join() to return, to ensure

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/16/18 7:33 PM, David Holmes wrote: Hi Dean, Thanks for tackling this. I'm still struggling to fully grasp why we need both the PerfCounters and the regular counters. I get that we have to decrement the live counts before ensure_join() has allowed Thread.join() to return, to ensure

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

Hi Dean, Thanks for tackling this. I'm still struggling to fully grasp why we need both the PerfCounters and the regular counters. I get that we have to decrement the live counts before ensure_join() has allowed Thread.join() to return, to ensure that if we then check the number of threads

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

New webrev: http://cr.openjdk.java.net/~dlong/8021335/webrev.4/ dl On 10/16/18 11:59 AM, dean.l...@oracle.com wrote: On 10/16/18 10:28 AM, JC Beyler wrote: Hi Dean, I noticed a typo here : "are atomically" is in the comment but should no longer be there I believe; the sentence probably

Re: RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

On 10/16/18 10:28 AM, JC Beyler wrote: Hi Dean, I noticed a typo here : "are atomically" is in the comment but should no longer be there I believe; the sentence probably should be: // These 2 counters are like the above thread counts, but are Fixed! Any way we could move this test into a

RFR(S) 8021335: Missing synchronization when reading counters for live threads and peak thread count

https://bugs.openjdk.java.net/browse/JDK-8021335 http://cr.openjdk.java.net/~dlong/8021335/webrev.3/ This change attempts to fix an old and intermittent problem with ThreadMXBean thread counts. Changes have 3 main parts: 1. Make sure hidden threads don't affect counts (even when exiting) 2.