Messages in this thread | | | Date | Tue, 25 Jul 2006 14:18:32 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] RTC: Add mmap method to rtc character driver |
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Jim Gettys wrote: > On Tue, 2006-07-25 at 14:04 -0700, H. Peter Anvin wrote: > >> That's why I'm suggesting adding a cheap, possibly low-res, gettimeofday >> virtual system call in case there is no way for the kernel to provide >> userspace with a cheap full-resolution gettimeofday. Obviously, if a >> high-quality gettimeofday is available, then they can be linked together >> by the kernel. > > Low res is fine: X Timestamps are 1 millisecond values, and wrap after a > few hundred days. What we do care about is monotonically increasing > values (until it wraps). On machines of the past, this was very > convenient; we'd just store a 32 bit value for clients to read, and not > bother with locking. I guess these days, you'd at least have to protect > the store with a memory barrier, maybe.... > > It was amusing years ago to find toolkit bugs after applications had > been up for that long (32 bits of milliseconds)... Yes, there are > applications and machines that stay up that long, really there are.... >
Do you need 1 ms resolution, or is 10 ms good enough?
-hpa
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