From: Bill H. <bha...@us...> - 2001-03-08 17:54:12
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Mike Kravetz wrote : > It seems obvious that the additional number of reschedules causes > lower numbers in this workload. I need to further examine this > situation. > Any comments or suggestions? > -- Mike, How much did the metric for "Henry" decrease with MQ ? I think we are running "Henry" also. Can you forward me the acg output file ? I wonder if priority preemptions are greater for MQ. Bill Hartner |
From: Hubertus F. <fr...@us...> - 2001-03-08 18:58:16
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I think there are some other reasons other then race conditions, why the (nr_pending > 0) is so much higher in vanilla then in MQ. Can you use my simple counter patch and figure out how much falls into the early buckets of nr_pending (<0, == 0, 1, 2, 3, 4, 4+). Maybe we can get some more information on whether its an offset problem, i.e. vanilla: 0+1 == MQ = 0+1 buckets. Hubertus Franke Mike Kravetz <mkr...@se...>@lists.sourceforge.net on 03/08/2001 01:33:24 PM Sent by: lse...@li... To: Bill Hartner/Austin/IBM@IBMUS cc: Lse-tech <lse...@li...> Subject: Re: [Lse-tech] Transactoin Processing Workload On Thu, Mar 08, 2001 at 12:55:48PM -0500, Bill Hartner wrote: > > Mike, > > How much did the metric for "Henry" decrease with MQ ? > I think we are running "Henry" also. > > Can you forward me the acg output file ? > > I wonder if priority preemptions are greater for MQ. > > Bill Hartner As a further update, I added some counters to sys_sched_yield and here are the results: 2.4.1 ----- sys_sched_yield calls 31107122 nr_pending > 0 6468740 nr_pending < 0 1986 nr_pending == 0 24636396 2.4.1-multi-queue ----------------- sys_sched_yield calls 24605235 nr_pending > 0 11990726 nr_pending < 0 633 nr_pending == 0 12613876 When nr_pending is non-zero, the 'need_resched' flag is set in the current process which results in a call to schedule. As you can see we have many more reschedules in the multi-queue scheduler. Also, it is interesting to note how 'racy' this code actually is by the number of times nr_pending evaluates to a negative number. I attempted to make the multi-queue version of sys_sched_yield functionally equivalent to the current version. However, in practice this does not seem to be the case. -- Mike Kravetz mkr...@se... IBM Linux Technology Center _______________________________________________ Lse-tech mailing list Lse...@li... http://lists.sourceforge.net/lists/listinfo/lse-tech |
From: Hubertus F. <fr...@us...> - 2001-03-08 19:42:08
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Chatting with Shailabh here.... we are wondering whether this is yet another example of a thundering herd, in the sense, that we get through some bottleneck in the app and many tasks are starting to run again at the same time, where in the vanilla case it takes a longer time to populate the runqueue again. That's kind of why I'd like to see a better distribution of nr_pending in the low range. It surprises me that nr_pending>=0 is actually smaller in the MQ case yet nr_pending>0 is higher in MQ. Hubertus Franke Hubertus Franke/Watson/IBM@IB...@li... on 03/08/2001 02:01:26 PM Sent by: lse...@li... To: Mike Kravetz <mkr...@se...> cc: Lse-tech <lse...@li...> Subject: Re: [Lse-tech] Transactoin Processing Workload I think there are some other reasons other then race conditions, why the (nr_pending > 0) is so much higher in vanilla then in MQ. Can you use my simple counter patch and figure out how much falls into the early buckets of nr_pending (<0, == 0, 1, 2, 3, 4, 4+). Maybe we can get some more information on whether its an offset problem, i.e. vanilla: 0+1 == MQ = 0+1 buckets. Hubertus Franke Mike Kravetz <mkr...@se...>@lists.sourceforge.net on 03/08/2001 01:33:24 PM Sent by: lse...@li... To: Bill Hartner/Austin/IBM@IBMUS cc: Lse-tech <lse...@li...> Subject: Re: [Lse-tech] Transactoin Processing Workload On Thu, Mar 08, 2001 at 12:55:48PM -0500, Bill Hartner wrote: > > Mike, > > How much did the metric for "Henry" decrease with MQ ? > I think we are running "Henry" also. > > Can you forward me the acg output file ? > > I wonder if priority preemptions are greater for MQ. > > Bill Hartner As a further update, I added some counters to sys_sched_yield and here are the results: 2.4.1 ----- sys_sched_yield calls 31107122 nr_pending > 0 6468740 nr_pending < 0 1986 nr_pending == 0 24636396 2.4.1-multi-queue ----------------- sys_sched_yield calls 24605235 nr_pending > 0 11990726 nr_pending < 0 633 nr_pending == 0 12613876 When nr_pending is non-zero, the 'need_resched' flag is set in the current process which results in a call to schedule. As you can see we have many more reschedules in the multi-queue scheduler. Also, it is interesting to note how 'racy' this code actually is by the number of times nr_pending evaluates to a negative number. I attempted to make the multi-queue version of sys_sched_yield functionally equivalent to the current version. However, in practice this does not seem to be the case. -- Mike Kravetz mkr...@se... IBM Linux Technology Center _______________________________________________ Lse-tech mailing list Lse...@li... http://lists.sourceforge.net/lists/listinfo/lse-tech _______________________________________________ Lse-tech mailing list Lse...@li... http://lists.sourceforge.net/lists/listinfo/lse-tech |
From: Mike K. <mkr...@se...> - 2001-03-08 18:31:49
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On Thu, Mar 08, 2001 at 12:55:48PM -0500, Bill Hartner wrote: > > Mike, > > How much did the metric for "Henry" decrease with MQ ? > I think we are running "Henry" also. > > Can you forward me the acg output file ? > > I wonder if priority preemptions are greater for MQ. > > Bill Hartner As a further update, I added some counters to sys_sched_yield and here are the results: 2.4.1 ----- sys_sched_yield calls 31107122 nr_pending > 0 6468740 nr_pending < 0 1986 nr_pending == 0 24636396 2.4.1-multi-queue ----------------- sys_sched_yield calls 24605235 nr_pending > 0 11990726 nr_pending < 0 633 nr_pending == 0 12613876 When nr_pending is non-zero, the 'need_resched' flag is set in the current process which results in a call to schedule. As you can see we have many more reschedules in the multi-queue scheduler. Also, it is interesting to note how 'racy' this code actually is by the number of times nr_pending evaluates to a negative number. I attempted to make the multi-queue version of sys_sched_yield functionally equivalent to the current version. However, in practice this does not seem to be the case. -- Mike Kravetz mkr...@se... IBM Linux Technology Center |