Hi Chris, The first stacktrace you are observing is for threadpool thread parking. We use this technique for threads that are currently not doing anything, to keep them around for a little while (5-60 seconds) so if we have burst of usage, we do not end up destroying and creating threads all the time.
The second stacktrace you are observing is, as you noted, when performing a garbage collection, when the GC thread is suspending all the running threads. So if you are witnessing this trace very often, it means a thread is allocating memory very quickly triggering GC collection very often. So I would need more information to tell you exactly why it would use 100% CPU. Also which version of Mono are you running? Thank you very much, Ludovic On Wed, May 25, 2016 at 8:30 PM Chris Swiedler <cswied...@trionworlds.com> wrote: > We have a server app which is periodically going into a mode where all > threadpool threads start running at very high CPU. I've run pstack when > it's in this mode, and every time I do it, nearly all the threadpool > threads have this stack: > > #0 pthread_cond_timedwait@@GLIBC_2.3.2 () at > ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238 > #1 0x0000000000618817 in mono_cond_timedwait_ms > (cond=cond@entry=0x7fe7ee1fddc0, > mutex=0x241eb78, timeout_ms=<optimized out>) at mono-mutex.c:181 > #2 0x0000000000586f28 in worker_park () at threadpool-ms.c:509 > #3 worker_thread (data=<optimized out>) at threadpool-ms.c:607 > #4 0x00000000005841e9 in start_wrapper_internal (data=<optimized out>) at > threads.c:725 > #5 start_wrapper (data=<optimized out>) at threads.c:772 > #6 0x0000000000621026 in inner_start_thread (arg=0x7fe831df4650) at > mono-threads-posix.c:97 > #7 0x00007fe88a55edf5 in start_thread (arg=0x7fe7ee1fe700) at > pthread_create.c:308 > #8 0x00007fe88a28c1ad in clone () at > ../sysdeps/unix/sysv/linux/x86_64/clone.S:113 > > Usually one thread will have a stack like this: > > #0 sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:85 > #1 0x000000000061aa37 in mono_sem_wait (sem=0x9542c0 > <suspend_ack_semaphore>, alertable=alertable@entry=0) at > mono-semaphore.c:107 > #2 0x00000000005c77bd in sgen_wait_for_suspend_ack (count=count@entry=18) > at sgen-os-posix.c:188 > #3 0x00000000005c78f9 in sgen_thread_handshake (suspend=suspend@entry=1) > at sgen-os-posix.c:224 > #4 0x00000000005c7e92 in sgen_client_stop_world > (generation=generation@entry=0) at sgen-stw.c:234 > #5 0x00000000005e6aca in sgen_stop_world (generation=0) at sgen-gc.c:3389 > #6 0x00000000005e6c29 in sgen_perform_collection (requested_size=4096, > generation_to_collect=0, reason=0x6d9595 "Nursery full", wait_to_finish=0) > at sgen-gc.c:2322#7 0x00000000005da62a in sgen_alloc_obj_nolock > (vtable=vtable@entry=0x7fe85c0343c0, size=size@entry=128) at > sgen-alloc.c:291 > #8 0x00000000005da913 in sgen_alloc_obj (vtable=vtable@entry=0x7fe85c0343c0, > size=128) at sgen-alloc.c:457 > #9 0x00000000005c86e9 in mono_gc_alloc_obj > (vtable=vtable@entry=0x7fe85c0343c0, > size=<optimized out>) at sgen-mono.c:936 > #10 0x00000000005a8b54 in mono_object_new_alloc_specific > (vtable=vtable@entry=0x7fe85c0343c0) at object.c:4385 > #11 0x00000000005a8bf0 in mono_object_new_specific (vtable=0x7fe85c0343c0) > at object.c:4379 > #12 0x00000000005a8c8c in mono_object_new (domain=domain@entry=0x1ded1c0, > klass=<optimized out>) at object.c:4318 > #13 0x00000000005ac1c9 in mono_async_result_new > (domain=domain@entry=0x1ded1c0, > handle=handle@entry=0x0, state=0x0, data=data@entry=0x0, > object_data=object_data@entry=0x7fe8838af020) at object.c:5768 > #14 0x00000000005887ff in mono_threadpool_ms_begin_invoke > (domain=0x1ded1c0, target=target@entry=0x7fe8838aee38, > method=method@entry=0x2963d28, > params=params@entry=0x7fe7ed9f8f10) at threadpool-ms.c:1300 > #15 0x000000000054b547 in mono_delegate_begin_invoke > (delegate=0x7fe8838aee38, params=0x7fe7ed9f8f10) at marshal.c:2111 > #16 0x00000000416d29d8 in ?? () > #17 0x0000000000000000 in ?? () > > Just from reading the first stack, it doesn't look like > mono_cond_timedwait_ms would spin, at least as long as the timeout_ms > wasn't 0. For the second stack, I don't know whether that's a normal > garbage collection pass or (since we see it frequently) a sign that garbage > collection is happening too often. > > Can anyone give me some pointers for where to dig more deeply? > > Thanks, > chris > _______________________________________________ > Mono-devel-list mailing list > Mono-devel-list@lists.ximian.com > http://lists.ximian.com/mailman/listinfo/mono-devel-list >
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