Chris - I am running a mac book pro. I will try to setup a simple test case when I get a chance and post the results.
On Wed, Nov 4, 2015 at 11:54 AM, Christopher Schultz <ch...@christopherschultz.net> wrote: > Farzad, > > On 11/3/15 2:45 PM, Farzad Panahi wrote: >> I wish I could get my hands on a real server : ) > > What computer do you use to access the server? That one will certainly > work for this kind of testing. > > -chris > >> 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 >>> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org >> For additional commands, e-mail: users-h...@tomcat.apache.org >> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org > --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
