Messages in this thread | | | Date | Fri, 26 Jun 2009 09:25:04 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: tsc based udelay should have rdtsc_barrier |
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* Pallipadi, Venkatesh <venkatesh.pallipadi@intel.com> wrote:
> > delay_tsc needs rdtsc_barrier to provide proper delay. > > Output from a test driver using hpet to cross check delay > provided by udelay(). > > Before: > [ 86.794363] Expected delay 5us actual 4679ns > [ 87.154362] Expected delay 5us actual 698ns > [ 87.514162] Expected delay 5us actual 4539ns > [ 88.653716] Expected delay 5us actual 4539ns > [ 94.664106] Expected delay 10us actual 9638ns > [ 95.049351] Expected delay 10us actual 10126ns > [ 95.416110] Expected delay 10us actual 9568ns > [ 95.799216] Expected delay 10us actual 9638ns > [ 103.624104] Expected delay 10us actual 9707ns > [ 104.020619] Expected delay 10us actual 768ns > [ 104.419951] Expected delay 10us actual 9707ns > > After: > [ 50.983320] Expected delay 5us actual 5587ns > [ 51.261807] Expected delay 5us actual 5587ns > [ 51.565715] Expected delay 5us actual 5657ns > [ 51.861171] Expected delay 5us actual 5587ns > [ 52.164704] Expected delay 5us actual 5726ns > [ 52.487457] Expected delay 5us actual 5657ns > [ 52.789338] Expected delay 5us actual 5726ns > [ 57.119680] Expected delay 10us actual 10755ns > [ 57.893997] Expected delay 10us actual 10615ns > [ 58.261287] Expected delay 10us actual 10755ns > [ 58.620505] Expected delay 10us actual 10825ns > [ 58.941035] Expected delay 10us actual 10755ns > [ 59.320903] Expected delay 10us actual 10615ns > [ 61.306311] Expected delay 10us actual 10755ns > [ 61.520542] Expected delay 10us actual 10615ns
Nice fix!
Ingo
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