Messages in this thread | | | Date | Mon, 12 Mar 2007 15:31:18 +0100 | From | Ingo Molnar <> | Subject | Re: [patch] change futex_wait() to hrtimers |
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* Theodore Tso <tytso@mit.edu> wrote:
> What we probably need in the long-term, and not just for high > precision wakeups, is we need a way for waiters (either in the kernel > or in userspace) to specify a desired precision in their timers. Is > it, "wake me up in a second, exactly", or "wake me up in a second, > plus or minus 10ms"? (or 50ms? or 100ms?).
such a facility exists already, see round_jiffies() and round_jiffies_relative(). There's some short blurb about it at:
http://kernelnewbies.org/LinuxChanges#head-513ceda14f5d8cf5b8a7c81d7e3821543141ecb0
> This becomes especially important if we want the tickless code to > really shine as far as power management is concerned. [...]
yes. That's why we also implemented /proc/timer_stat, and this was measured and a few higher-frequency fuzzy waiters were converted to use round_jiffies(). Some other waiters were fixed in user-space. It's all dependent on actual measurements and circumstances.
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