Messages in this thread | | | Subject | Re: [patch] voluntary-preempt-2.6.8-rc2-M5 | From | Lee Revell <> | Date | Sun, 01 Aug 2004 14:08:16 -0400 |
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On Sun, 2004-08-01 at 07:28, Ingo Molnar wrote: > On Fri, 30 Jul 2004, Lee Revell wrote: > > > Results with 2.6.8-rc2-M5: > > > > Configuration max usecs > > ----------------------------------------------------------------- > > All IRQs threaded 370 > > Soundcard IRQ not threaded 335 > > Soundcard IRQ not threaded + max_sectors_kb -> 64 161 > > > > So, it looks like the added configurability does add some overhead - 161 > > usecs vs. 50. [...] > > +110 usecs is too much to be explained by redirection and configurability > overhead. The configurability overhead is near zero. > > could you try to repeat the '50 usecs' test with -L2 [that was the one you > used?] to make sure it's repeatable? The latencies of -L2 and -M5 should > be near identical. The configurability should at most cause a 1-2 usecs > overhead - definitely not two orders of magnitude higher. So if there's a > difference then i must have degraded one of the latency reduction changes > between L2 and M5.
The above numbers really do not tell you much, I have some better ones. Here is the histogram for a 5,000,000 sample run with M5:
Delay Count ----- ----- 6 98189 7 2013275 8 51025 9 120465 10 93339 11 72087 12 116165 13 106433 14 85930 15 57178 16 59835 17 51096 18 71671 19 106738 20 109491 21 84906 22 2215 23 946 24 1755 25 1977 26 1589 27 1117 28 1889 29 1616 30 1858 31 2926 32 3111 33 2558 34 400 35 1366 36 2172 37 2840 38 1088 39 1042 40 172 41 26 42 32 43 43 44 41 45 10 46 8 47 36 48 109 49 125 50 83 51 45 52 36 53 7 55 1 56 1 58 1 61 1 62 1 68 1 75 1 77 1 79 1 89 1 97 1
So if you discard the highest ~10 of 5,000,000, it's the same as L2. Maybe a corner case, or a new race condition? I will run the above test with L2.
I wonder if the multiple spikes represent different code paths, or the same but with a hot/warm/cold cache?
Lee
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