Hi,
Without the support of High Resolution Timer supported,
the timer resolution wouldn't change.
With high-resolution-timer supported,
our arm926-based board could get resolution like 40~50us.
There are codes you can reference ,may be you should just try to implement it.
JFI, Thanks.
From: tike64 <[email protected]>
Subject: realtime-preempt and arm
Date: Wed, 29 Nov 2006 00:57:05 -0800 (PST)
> Hi all,
>
> I'm trying the realtime-preempt patch-2.6.18-rt6 on
> lh7a400 arm system with little success. In a test
> program I try 5 ms timeout with select() but get 20 ms
> avg or 26 ms max. When the framebuffer scrolls, the
> max delay goes up to 59 ms. With a vanilla kernel I
> get 10 ms (because of tick resolution?), 11 ms and 39
> ms.
>
> My question is, is the realtime-preempt patch supposed
> to work on arm architecture and/or without high
> resolution timer (which lh7a40x seems to lack) at all
> or should I just try to be more clever.
>
> Relevant code:
>
> ====
> prio.sched_priority = 99;
> if (sched_setscheduler(0, SCHED_RR, &prio) < 0) ...
> if (mlockall(MCL_CURRENT | MCL_FUTURE) < 0) ...
> while (1) {
> t = raw_timer();
> tv.tv_usec = 5000;
> tv.tv_sec = 0;
> select(0, 0, 0, 0, &tv);
> t = raw_timer() - t;
> if (max_t < t) max_t = t;
> if (min_t > t) min_t = t;
> avg_t += t;
> ++n;
> if (n < 100) continue;
> printf("%i revs; min: %i max: %i avg: %i\n",
> n,
> min_t,
> max_t,
> (avg_t + n / 2) / n);
> ====
>
> Relevant config: PREEMPT_RT, PREEMPT_SOFTIRQS,
> PREEMPT_HARDIRQS
>
> I didnt' enable HIGH_RES_TIMERS because lh7a40x seems
> not to support it.
>
> --
>
> tike
>
>
>
>
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