Re: [PATCH] poll: Avoid extra wakeups in select/poll

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To: Eric Dumazet <dada1@...>
Cc: Christoph Lameter <cl@...>, linux kernel <linux-kernel@...>, Andi Kleen <andi@...>, David Miller <davem@...>, <jesse.brandeburg@...>, <netdev@...>, <haoki@...>, <mchan@...>, <davidel@...>
Date: Wednesday, April 29, 2009 - 5:11 am

* Eric Dumazet <dada1@cosmosbay.com> wrote:


very nice. It might not show up as a real performance difference if 
the CPUs are not fully saturated during the test - but it could show 
up as a decrease in CPU utilization.

Also, if you run the test via 'perf stat -a ./test.sh' you should 
see a reduction in instructions executed:

aldebaran:~/linux/linux> perf stat -a sleep 1

 Performance counter stats for 'sleep':

   16128.045994  task clock ticks     (msecs)
          12876  context switches     (events)
            219  CPU migrations       (events)
         186144  pagefaults           (events)
    20911802763  CPU cycles           (events)
    19309416815  instructions         (events)
      199608554  cache references     (events)
       19990754  cache misses         (events)

 Wall-clock time elapsed:  1008.882282 msecs

With -a it's measured system-wide, from start of test to end of test 
- the results will be a lot more stable (and relevant) statistically 
than wall-clock time or CPU usage measurements. (both of which are 
rather imprecise in general)

	Ingo
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Messages in current thread:
udp ping pong with various process bindings (and correct cpu..., Christoph Lameter, (Fri Apr 24, 4:10 pm)
[PATCH] poll: Avoid extra wakeups, Eric Dumazet, (Sun Apr 26, 6:46 am)
Re: [PATCH] poll: Avoid extra wakeups, Andi Kleen, (Tue Apr 28, 10:21 am)
[PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Tue Apr 28, 11:06 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Ingo Molnar, (Wed Apr 29, 5:16 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Wed Apr 29, 5:36 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Ingo Molnar, (Wed Apr 29, 6:27 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Wed Apr 29, 8:29 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Davide Libenzi, (Wed Apr 29, 11:53 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Ingo Molnar, (Wed Apr 29, 9:07 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Andrew Morton, (Wed Apr 29, 3:20 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Wed Apr 29, 3:39 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Wed Apr 29, 4:26 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Andi Kleen, (Wed Apr 29, 3:35 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Ingo Molnar, (Wed Apr 29, 5:22 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Wed Apr 29, 3:37 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Christoph Lameter, (Tue Apr 28, 3:05 pm)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Tue Apr 28, 4:05 pm)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Christoph Lameter, (Tue Apr 28, 4:14 pm)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Tue Apr 28, 4:33 pm)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Christoph Lameter, (Tue Apr 28, 4:49 pm)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Tue Apr 28, 5:04 pm)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Tue Apr 28, 5:11 pm)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Ingo Molnar, (Wed Apr 29, 5:11 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Thu Apr 30, 6:49 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Ingo Molnar, (Thu Apr 30, 7:57 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Thu Apr 30, 10:08 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Paul E. McKenney, (Thu Apr 30, 5:24 pm)
[BUG] perf_counter: change cpu frequencies , Eric Dumazet, (Thu Apr 30, 12:07 pm)
Re: [BUG] perf_counter: change cpu frequencies, Eric Dumazet, (Sun May 3, 2:06 am)
Re: [BUG] perf_counter: change cpu frequencies, Ingo Molnar, (Sun May 3, 3:25 am)
Re: [BUG] perf_counter: change cpu frequencies, Eric Dumazet, (Mon May 4, 6:39 am)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Christoph Lameter, (Tue Apr 28, 5:00 pm)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Eric Dumazet, (Tue Apr 28, 5:05 pm)
Re: [PATCH] poll: Avoid extra wakeups in select/poll, Christoph Lameter, (Tue Apr 28, 5:04 pm)
Re: [PATCH] poll: Avoid extra wakeups, Eric Dumazet, (Tue Apr 28, 10:58 am)
Re: [PATCH] poll: Avoid extra wakeups, David Miller, (Tue Apr 28, 5:15 am)
Re: [PATCH] poll: Avoid extra wakeups, Eric Dumazet, (Tue Apr 28, 5:24 am)
Re: [PATCH] poll: Avoid extra wakeups, Jarek Poplawski, (Sun Apr 26, 9:33 am)
Re: [PATCH] poll: Avoid extra wakeups, Eric Dumazet, (Sun Apr 26, 10:27 am)