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 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
covers thread termination but couldn't see anything specific.
Can you at least run this through our performance system to see
if any of the regular benchmarks are affected.
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 get_live_thread_count() { MutexLocker
mu(Threads_lock); return _live_threads_count->get_value() -
_exiting_threads_count; }
static jlong get_daemon_thread_count() { MutexLocker
mu(Threads_lock); return _daemon_threads_count->get_value() -
_exiting_daemon_threads_count; }
along with the other cleanups around is_daemon and is_hidden_thread?
Some micro-benchmarks like SecureRandomBench show a regression
with webrev.7. I could go back to webrev.5 and then we shouldn't
need any locking in the get_*() functions.
I don't see version 5 discussed but I took a look and it seems okay.
Mandy had questions about the asserts in .5, and it seemed like we
could just set the perf counters to the same value as the atomic
counters, which resulted in .6. I think the only problem with .6 is
that I set the perf counters in decrement_thread_counts without the
lock. If I "sync" the perf counters to the atomic counters only in
add_thread and remove_thread, with the lock, then it's about the
same as .5, but without the asserts and parallel inc/dec. If anyone
likes the sound of that, I can send out a new webrev. Or we can go
with webrev.5.
I'm not sure what the concern was with the asserts - if they mis-fire
we'll know soon enough. So I'm okay with .5
My only query with that version is that it appears the actual
perfCounters no longer get read by anything - is that the case?
There does seem to be code that references them, through their name
string. That's a difference interface that I'm not familiar with,
so I didn't want to break it.
Right - they can be accessed directly through other means. I was
concerned that the perfCounter was out of sync with
get_live_thread-count() but that's already the case so not an issue.
If all tests and benchmarks are happy I say go with version .5
I have no objection to version .5 if most people prefer that. My
comment was that I don't think the asserts are necessary.
OK, I'll rerun some performance benchmarks and push .5 if the results
look OK. David, can you send me your micro-benchmark?
Thanks for the reviews!
dl
Mandy
