Re: SMP performance degradation with sysbench

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From: Andrea Arcangeli
Date: Tuesday, March 13, 2007 - 3:57 am

On Tue, Mar 13, 2007 at 09:37:54PM +1100, Nick Piggin wrote:

So it again makes little sense to me that this is idle time, unless
some userland mutex has a usleep in the slow path which would be very
wrong, in the worst case they should yield() (yield can still waste
lots of cpu if two tasks in the slow paths calls it while the holder
is not scheduled, but at least it wouldn't be idle time).

Idle time is suspicious for a kernel issue in the scheduler or some
userland inefficiency (the latter sounds more likely).
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Messages in current thread:
SMP performance degradation with sysbench, Lorenzo Allegrucci, (Sun Feb 25, 10:44 am)
Re: SMP performance degradation with sysbench, Rik van Riel, (Sun Feb 25, 4:46 pm)
Re: SMP performance degradation with sysbench, Nick Piggin, (Mon Feb 26, 6:36 am)
Re: SMP performance degradation with sysbench, Nick Piggin, (Mon Feb 26, 6:41 am)
Re: SMP performance degradation with sysbench, Pete Harlan, (Mon Feb 26, 3:04 pm)
Re: SMP performance degradation with sysbench, Dave Jones, (Mon Feb 26, 3:36 pm)
Re: SMP performance degradation with sysbench, Hiro Yoshioka, (Mon Feb 26, 5:32 pm)
Re: SMP performance degradation with sysbench, Rik van Riel, (Mon Feb 26, 5:43 pm)
Re: SMP performance degradation with sysbench, Hiro Yoshioka, (Mon Feb 26, 9:03 pm)
Re: SMP performance degradation with sysbench, Rik van Riel, (Mon Feb 26, 9:31 pm)
Re: SMP performance degradation with sysbench, J.A. , (Tue Feb 27, 1:14 am)
Re: SMP performance degradation with sysbench, Rik van Riel, (Tue Feb 27, 7:02 am)
Re: SMP performance degradation with sysbench, Paulo Marques, (Tue Feb 27, 7:56 am)
Re: SMP performance degradation with sysbench, Lorenzo Allegrucci, (Tue Feb 27, 12:05 pm)
Re: SMP performance degradation with sysbench, Nish Aravamudan, (Tue Feb 27, 1:40 pm)
Re: SMP performance degradation with sysbench, Nish Aravamudan, (Tue Feb 27, 6:27 pm)
Re: SMP performance degradation with sysbench, Bill Davidsen, (Tue Feb 27, 7:21 pm)
Re: SMP performance degradation with sysbench, Nick Piggin, (Tue Feb 27, 7:22 pm)
Re: SMP performance degradation with sysbench, Nish Aravamudan, (Tue Feb 27, 7:51 pm)
Re: SMP performance degradation with sysbench, Nish Aravamudan, (Tue Feb 27, 7:52 pm)
Re: SMP performance degradation with sysbench, Nish Aravamudan, (Wed Feb 28, 5:20 pm)
Re: SMP performance degradation with sysbench, Lorenzo Allegrucci, (Thu Mar 1, 9:57 am)
Re: SMP performance degradation with sysbench, Anton Blanchard, (Mon Mar 12, 3:00 pm)
Re: SMP performance degradation with sysbench, Nick Piggin, (Mon Mar 12, 10:11 pm)
Re: SMP performance degradation with sysbench, Eric Dumazet, (Mon Mar 12, 11:00 pm)
Re: SMP performance degradation with sysbench, Andrea Arcangeli, (Tue Mar 13, 2:45 am)
Re: SMP performance degradation with sysbench, Nick Piggin, (Tue Mar 13, 3:06 am)
Re: SMP performance degradation with sysbench, Andrea Arcangeli, (Tue Mar 13, 3:31 am)
Re: SMP performance degradation with sysbench, Nick Piggin, (Tue Mar 13, 3:37 am)
Re: SMP performance degradation with sysbench, Andrea Arcangeli, (Tue Mar 13, 3:57 am)
Re: SMP performance degradation with sysbench, Nick Piggin, (Tue Mar 13, 4:12 am)
Re: SMP performance degradation with sysbench, Eric Dumazet, (Tue Mar 13, 4:40 am)
Re: SMP performance degradation with sysbench, Andrea Arcangeli, (Tue Mar 13, 4:42 am)
Re: SMP performance degradation with sysbench, Nick Piggin, (Tue Mar 13, 4:56 am)
Re: SMP performance degradation with sysbench, Eric Dumazet, (Tue Mar 13, 5:02 am)
Re: SMP performance degradation with sysbench, Nick Piggin, (Tue Mar 13, 5:08 am)
Re: SMP performance degradation with sysbench, Jakub Jelinek, (Tue Mar 13, 5:27 am)
Re: SMP performance degradation with sysbench, Nish Aravamudan, (Tue Mar 13, 5:36 pm)
Re: SMP performance degradation with sysbench, Eric Dumazet, (Tue Mar 13, 6:00 pm)
Re: SMP performance degradation with sysbench, Nish Aravamudan, (Tue Mar 13, 6:09 pm)
Re: SMP performance degradation with sysbench, Siddha, Suresh B, (Wed Mar 14, 4:33 pm)
Re: SMP performance degradation with sysbench, Zhang, Yanmin, (Mon Mar 19, 7:29 pm)
Re: SMP performance degradation with sysbench, Zhang, Yanmin, (Sun Apr 1, 7:59 pm)