Hi Markus!
The priority of the exiting thread will be raised for quite a short
period of time -- right before the thread finishes exiting.
There are two places where the priority is adjusted.
Under normal conditions we should never see the first place hit.
However, if we do, this means we have a huge number of threads.
Raising the priority of one of them is a hint about which thread we want
the scheduler to focus on.
The second place is a bit different.
We have several threads running immediately before ending the process.
Some of them are at the exiting path and block exiting of the whole process.
Raising the priority of those threads is a way to say we're not
interested in all the other threads, as they are going to be terminated
anyway.
I just noticed that in second scenario it may be appropriate to set the
priority of the current thread to the same level as for the exiting threads.
This way it'll be given a fair chance to continue if the timeout expires.
I also think it should be enough to set the priority level to
THREAD_PRIORITY_ABOVE_NORMAL instead of THREAD_PRIORITY_HIGHEST.
It will give just +1 to the priority value -- should be enough for the hint.
Would you please take a look at the updated webrev:
http://cr.openjdk.java.net/~igerasim/8064694/2/webrev/
Sincerely yours,
Ivan
On 17.11.2014 11:33, Markus Grönlund wrote:
I agree with David.
The side effects will be unknown and very hard to debug.
Is there another way to accomplish the results without manipulating base
services?
Thanks
Markus
-----Original Message-----
From: David Holmes
Sent: den 17 november 2014 07:40
To: Ivan Gerasimov; Daniel Daugherty
Cc: serviceability-dev@openjdk.java.net; hotspot-runtime-dev
Subject: Re: RFR 8064694: Kitchensink: WaitForMultipleObjects failed in
hotspot\src\os\windows\vm\os_windows.cpp: 3844
On 17/11/2014 7:23 AM, Ivan Gerasimov wrote:
Thank you Daniel!
Please find the updated webrev with your suggestions incorporated here:
http://cr.openjdk.java.net/~igerasim/8064694/1/webrev/
Concerning the thread priority: If the application is of
NORMAL_PRIORITY_CLASS, then setting the thread's priority level to
THREAD_PRIORITY_HIGHEST will result in its priority value to be only
10 (of maximum 31).
http://msdn.microsoft.com/en-us/library/windows/desktop/ms685100(v=vs.
85).aspx
And if the process is HIGH_PRIORITY_CLASS, then the tread with the
HIGHEST priority level will have priority value == 15 of 31.
I believe, it should not be too much, and the machine will not become
busy with only those closing threads.
However, I hope it would be enough to make them complete faster than
other threads of the NORMAL priority level withing the same application.
I don't think this is necessary or desirable. Under normal usage we're giving priority to
exiting threads and that may disrupt the usual scheduling patterns that applications see.
You may posit that it is "harmless" but we can't say that for sure. Nor can we
actually know that this will help with this particular bug. I would not add in this new
code.
David
Sincerely yours,
Ivan
On 15.11.2014 2:22, Daniel D. Daugherty wrote:
On 11/14/14 5:35 AM, Ivan Gerasimov wrote:
Hello!
The recent fix for JDK-8059533 ((process) Make exiting process wait
for exiting threads [win]) caused the warning message to be printed
in some test environments:
-----------
os_windows.cpp:3844 is in the newly updated
os::win32::exit_process_or_thread(Ept what, int exit_code)
-----------
This has been observed with debug builds on highly loaded systems.
To address the issue it is proposed to do three things:
1) increase the timeout for debug builds,
2) increase the maximum number of the thread handles to be stored,
3) rise the priority of the exiting threads, if we need to wait for
them.
Would you please help review the fix?
BUGURL: https://bugs.openjdk.java.net/browse/JDK-8064694
WEBREV: http://cr.openjdk.java.net/~igerasim/8064694/0/webrev/
src/os/windows/vm/os_windows.cpp
line 3784: #define MAX_EXIT_HANDLES NOT_DEBUG(32) DEBUG_ONLY(128)
Instead of NOT_DEBUG can you use PRODUCT_ONLY?
Instead of DEBUG_ONLY can you used NOT_PRODUCT?
That uses the smaller value for only one build config (PRODUCT).
line 3785: #define EXIT_TIMEOUT NOT_DEBUG(1000) DEBUG_ONLY(4000)
/*1 sec in product, 4 sec in debug*/
Instead of NOT_DEBUG can you use PRODUCT_ONLY?
Instead of DEBUG_ONLY can you used NOT_PRODUCT?
Please add spaces between the comment delimiters and the comment
text.
That uses the smaller timeout for only one build config (PRODUCT).
line 3836 // Rise the priority...
Typo: 'Rise' -> 'Raise'
About the general idea of raising the exiting thread's priority,
if the exiting thread is looping in some Win* OS code after this
point, will raising the priority make the machine unusable?
Dan
The fix was tested on all available platforms, with the hotspot
testset. No failures.
Sincerely yours,
Ivan
