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Rockbox mail archiveSubject: Re: X11 simulator clock runs too fastRe: X11 simulator clock runs too fast
From: c s <rb_dev_at_yahoo.com>
Date: Thu, 6 Mar 2003 17:42:23 -0800 (PST) --- Daniel Stenberg <daniel_at_haxx.se> wrote: > On Thu, 6 Mar 2003, Jerry Van Baren wrote: > > > There is a high resolution timer patch for linux: > > > It works very well. I don't know if it has been > accepted into the > > mainstream kernel yet. > > As I was saying, we should not write anything to > depend on any kind of high > resolution timers in the simulator. It would be > totally pointless and counter > productive. > You are right. There isn't much of a point trying to make the simulator clock highly accurate since some or all of the periodic rockbox threads are of the form: while(1) { do_something(); sleep(some_num_ticks); } ...so the period of the task in terms of ticks depends both on how long it takes to execute the do_something() on the simulator hardware as well as the accuracy the clock emulation. Even with a highly accurate simulated tick, the period of rockbox tasks can differ still differ depending on the speed of the simulator the code is running on. That being said, it is still desirable to try to achieve a somewhat accurate tick in the simulator if we can do it without making the simulator code non-portable. Currently it runs 10 times too fast, on the system I run on, so all the places in the rockbox code that check on an elapsed time by doing "TIME_AFTER(current_tick, xxx)" are off by a factor of 10. When I change the increment value in x11_sleep form 5 to 'tics', then current_tick runs about 3 times too fast (because of the problem that I discussed earlier where multiple threads can be in a sleep call and all will be incrementing current_tick). The best quick fix seems to be to change the increment value in x11_sleep from 5 to 1. This works fairly well because no matter what rockbox is doing, there is always a thread doing constant calls to button_get_w_timeout which does multiple calls of sleep(1) to do its timeout. __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/ Received on 2003-03-07 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |