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From "Weldon Washburn" <weldon...@gmail.com>
Subject Re: [drlvm][thread]scalability problem
Date Mon, 24 Sep 2007 16:29:28 GMT
On 9/24/07, Yuri Dolgov <dolgov.g.yuri@gmail.com> wrote:
> Hello,
>
> I've identified the most probable reason of the issue. It concerns to
> gathering profiling information and absence of on stack replacement
> mechanism.

This is very interesting.  Good work!  I had no idea "on stack
replacement" code could cause such problems.


>
> Currently profiling data is gathered even after it is not
> needed any more for recompilation. And since there is no on stack
> replacement mechanism there is overhead on collection profile data
> till the end of the test. The problem could be solved by switching of
> the profile counters after they are not useful.
>
> BTW I'm using pretty fresh version of Harmony (release build) and
> can reproduce Cyang's problem.
>
> Thanks,
> Yuri
>
> On 9/24/07, Weldon Washburn <weldonwjw@gmail.com> wrote:
> >
> > Cyang, Yuri,
> >
> > I have committed several threading patches since M2 was released.
> > These threading patches might impact the performance of your test
> > below.  Are you using release build or debug build?
> >
> > I noticed your test uses Thread.join().  There are several known bugs
> > in Thread.join() that we hope to fix shortly. We are working on the
> > list of threading problems described in April 2 email called,
> > "[drlvm][threading] a list of design/development issues that need
> > coordination with the [general] "M1" map".  In particular we hope to
> > have, "Varying Mutexes Protect Different Parts of Thread State, Each
> > Thread Has Its Own Mutex" done in the next few months.  In other
> > words, before M4 or M5 is released.  This project (also called Thread
> > State Transition Project) intends to fix known Thread.join() problems.
> >
> > If you have the time, please try again with what is in svn HEAD.  Or
> > perhaps wait until M3 is released shortly.
> >
> > On 9/24/07, cyang.cq <cyang.cq@gmail.com> wrote:
> > > Hi, all
> > > The scalability of the program below is surprising on M2.
> > > This program only starts several threads to share the work
> > > of doing a number of additions.
> > >
> > > MT.java:
> > >
> > > public class MT extends Thread{
> > >
> > >  static long result = 0;
> > >  long len = 0;
> > >  public MT(long len){
> > >   this.len = len;
> > >  }
> > >
> > >  public void run(){
> > >  long total = 0;
> > >  for(long i = 0; i < len; ++i){
> > >     total += 1;
> > >  }
> > >  result = total;
> > >  }
> > >
> > >  public static void main(String[] args) throws InterruptedException {
> > >  long totalWork = Long.parseLong(args[0]);
> > >  int numThreads = Integer.parseInt(args[1]);
> > >
> > >  long work = totalWork / numThreads;
> > >
> > >  MT[] v = new MT[numThreads];
> > >  for(int i = 0; i < numThreads; ++i){
> > >   v[i] = new MT(work);
> > >  }
> > >
> > >  long start = System.currentTimeMillis();
> > >  for(int i = 0; i < numThreads; ++i){
> > >   v[i].start();
> > >  }
> > >  for(int i = 0; i < numThreads; ++i){
> > >    v[i].join();
> > >  }
> > >  long dur = System.currentTimeMillis() - start;
> > >
> > >  System.out.println("Total time: " + dur);
> > >  }
> > >
> > > }
> > >
> > > Run it on 5.0M2:
> > > CMD                        OUTPUT
> > > java MT 9000000000 1       Total time: 411325
> > > java MT 9000000000 2       Total time: 1052861
> > > java MT 9000000000 4       Total time: 915545
> > > java MT 9000000000 8       Total time: 589672
> > > java MT 9000000000 12      Total time: 678815
> > > java MT 9000000000 16      Total time: 621097
> > >
> > >
> > > Run it on sun jdk 1.5.0_08:
> > > CMD                       OUTPUT
> > > java MT 9000000000 1      Total time: 10356
> > > java MT 9000000000 2      Total time: 5182
> > > java MT 9000000000 4      Total time: 2601
> > > java MT 9000000000 8      Total time: 1453
> > > java MT 9000000000 12     Total time: 1004
> > > java MT 9000000000 16     Total time: 782
> > >
> > >
> > >
> > > My configuration is:
> > > OS:    Red Hat Enterprise Linux AS release 4 (Nahant Update 4)
> > >       Kernel 2.6.9-42.ELlargesmp on an x86_64
> > > CPU:   8 X Dual-Core AMD Opteron 2.6G
> > > Mem:   16G
> > > drlvm:  Apache Harmony 5.0M2 JRE for 32-bit Linux
> > >        for systems with libstdc++.so.5
> > > sun jdk: jdk-1_5_0_08-linux-i586
> > >
> > >
> > > Any suggestions? Have this been fixed already since M2?
> > >
> > > Thanks in advance.
> >
> >
> > --
> > Weldon Washburn
> >
>


-- 
Weldon Washburn

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