I wish I could get my hands on a real server : ) On Mon, Nov 2, 2015 at 12:23 PM, David kerber <dcker...@verizon.net> wrote: > On 11/2/2015 3:09 PM, Farzad Panahi wrote: >> >> Quoting from David Holme's blog: >> >>> The nanoTime method uses the highest resolution clock available on the >>> platform, and while its return value is in nanoseconds, the update >>> resolution is typically only microseconds. >> >> https://blogs.oracle.com/dholmes/entry/inside_the_hotspot_vm_clocks >> >> I think we can rely on nanoTime as a clock with microsecond >> resolution. Having said that can't we say printing out nanoTime in >> websocket message handler will give us a fair number (with microsecond >> accuracy) to measure how quickly the message handler is being called? >> >> All I am saying is that I see an obvious hiccup in order of >> milliseconds when threads are switching which I have no explanation >> for. >> >> Please advise if you think the way I am measuring is wrong. > > > I'm with Chris on this one: I think it's due to running on a VM rather than > on real hardware. > > > >> >> Cheers >> >> Farzad >> >> On Mon, Nov 2, 2015 at 4:56 AM, David kerber <dcker...@verizon.net> wrote: >>> >>> On 10/31/2015 10:51 AM, David Balažic wrote: >>>> >>>> >>>> Just a note: When most of you say "resolution" what you think about is >>>> actually called "accuracy". >>>> (also see "precision" , here is a good roundup: >>>> http://www.tutelman.com/golf/measure/precision.php ) >>> >>> >>> >>> I'm not sure about the others, but as an Electrical Engineer, I know the >>> difference between resolution, precision, and accuracy. In the post I >>> made >>> earlier, I said and meant "resolution". >>> >>> >>> >>> >>>> >>>> David Balažic >>>> Software Engineer >>>> www.comtrade.com >>>> >>>>> -----Original Message----- >>>>> From: Konstantin Preißer [mailto:kpreis...@apache.org] >>>>> Sent: 31. October 2015 10:27 >>>>> To: Tomcat Users List >>>>> Subject: [OT] RE: 80ms delay switching between worker threads >>>>> Importance: Low >>>>> >>>>> Hi Christopher, >>>>> >>>>>> -----Original Message----- >>>>>> From: Christopher Schultz [mailto:ch...@christopherschultz.net] >>>>>> Sent: Saturday, October 31, 2015 3:43 AM >>>>>> >>>>>> What OS are you using? IIRC, the Windows timer has horrible >>>>>> resolution. >>>>>> you can call System.currentTimeNanos all you want, but you won't get >>>>>> anything meaningful lower than some threshold regardless of the actual >>>>>> least significant digits coming back from those calls. >>>>> >>>>> >>>>> >>>>> While that may have been true in ancient versions like XP and Vista, at >>>>> least >>>>> starting with Win7 QueryPerformanceCounter() uses the processor's TSC >>>>> [1] >>>>> (where Vista used the HPET if available) so you should have a very high >>>>> resolution here. E.g. running the following Java program: >>>>> >>>>> int[] iterations = { 100, 120, 150, 250 }; >>>>> >>>>> for (int i = 0; i < iterations.length; i++) { >>>>> for (int j = 0; j < 3; j++) { >>>>> long currentTime = System.nanoTime(); >>>>> double startValue = 1000; >>>>> for (int z = 0; z < iterations[i]; z++) { >>>>> startValue = Math.pow(startValue, 0.99); >>>>> } >>>>> long difference = System.nanoTime() - currentTime; >>>>> System.out.println(iterations[i] + " pow iterations ms >>>>> took >>>>> " + >>>>> (difference / 1000L) + " µs"); >>>>> } >>>>> } >>>>> >>>>> prints on my system something like: >>>>> >>>>> 100 pow iterations ms took 25 µs >>>>> 100 pow iterations ms took 7 µs >>>>> 100 pow iterations ms took 7 µs >>>>> 120 pow iterations ms took 8 µs >>>>> 120 pow iterations ms took 9 µs >>>>> 120 pow iterations ms took 8 µs >>>>> 150 pow iterations ms took 11 µs >>>>> 150 pow iterations ms took 10 µs >>>>> 150 pow iterations ms took 13 µs >>>>> 250 pow iterations ms took 18 µs >>>>> 250 pow iterations ms took 17 µs >>>>> 250 pow iterations ms took 17 µs >>>>> >>>>> >>>>> So there should at least be a microsecond resolution. On a C# program >>>>> using >>>>> Stopwatch I get similar results in the range from 5 to 12 µs. >>>>> >>>>> Note, QueryPerformanceFrequency() [2] can be used to get the frequency >>>>> of the timer which is exposed in .Net through static >>>>> System.Diagnostics.Stopwatch.Frequency field as ticks per second. On my >>>>> system it prints "3323580" so the resolution should be around ~0.3 >>>>> microseconds. >>>>> >>>>> >>>>> Regards, >>>>> Konstantin Preißer >>>>> >>>>> [1] https://msdn.microsoft.com/en- >>>>> us/library/windows/desktop/dn553408%28v=vs.85%29.aspx >>>>> [2] https://msdn.microsoft.com/de- >>>>> de/library/windows/desktop/ms644905%28v=vs.85%29.aspx > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org >
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