victor jimenez <betaband...@gmail.com> wrote on 05/19/2009 09:25:38 AM:
> Hello, > > I realized that the log may not look nicely, so I am attaching it as a > text file. > > Victor > > On Tue, May 19, 2009 at 6:17 PM, victor jimenez <betaband...@gmail.com> wrote: > > Hello, > > > > I am using perfmon2 on IBM POWER5. > > The version I am using is libpfm 3.8 with kernel 2.6.28 (February > > 19th, 2009 release). > > > > My problem is that between two consecutives readings of the counters I > > get decreasing values. For instance, I want to read the number of > > misses in L2, so I read the counter PM_DATA_FROM_L2MISS. In reading > > 'i' I get 59695 and in reading 'i+1' I get 59637. > > > > I am wondering if this is a bug or it is some sort of limitation. > > However, in my opinion it looks like a bug. > > > > In order to understand what was going on, I modified the kernel to > > print some messages. In the log at the end of the mail the meaning of > > the fields in every line is: > > > > pfm_xxx : the function from where the message is printed > > pid : pid of the process which is printing the message > > task : parameter task which is present in some perfmon2 functions > > ctx : parameter/variable task which is present in some perfmon2 functions > > cnum : counter number > > value : value which is being written into the PMDS > > result : value readed from the PMDS > > > > About the pid field, in my experiment I am running two processes > > (2488, 2489) only 2489 is using perfmon2 (i.e., there is only one > > pfm_context). > > > > In my opinion, the problem comes because perfmon2 sometimes does not > > save PMDS right before a context switch. > > > > For instance, in the next log, at line 1 process 2489 is switched out > > and in line 6 and 8 pfm_save_pmds is called. The value which is being > > saved for counter 3 is 58339. At line 20 the user reads the counter > > with the call to sys_pfm_read_pmds and the value returned is 59695. > > > > The problem is that at line 26 when process 2489 is switched out > > again, the PMDS are not saved. And they are being restored at line 30 > > with the old value which was saved before (58339). > > > > After that, the counters keep increasing until we read them again at > > line 103. The value read there is 59637, which is smaller than the > > previous reading (59695). > > [snip] Hello Victor, Thank you very much for reporting this. You are right that it does appear to be a bug. I will look into this tomorrow. Thank you for providing such detailed information. Just to be clear, we are talking about Power5, right? The subject line says Power6, but that appears to be a typo, given the log you have provided. Regards, - Corey Corey Ashford Software Engineer IBM Linux Technology Center, Linux Toolchain Beaverton, OR 503-578-3507 cjash...@us.ibm.com ------------------------------------------------------------------------------ Crystal Reports - New Free Runtime and 30 Day Trial Check out the new simplified licensing option that enables unlimited royalty-free distribution of the report engine for externally facing server and web deployment. http://p.sf.net/sfu/businessobjects _______________________________________________ perfmon2-devel mailing list perfmon2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
