Messages in this thread | | | Date | Tue, 26 Feb 2002 13:50:06 -0700 | From | Andreas Dilger <> | Subject | Re: [patch][rfc] enable uptime display > 497 days on 32 bit |
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On Feb 26, 2002 11:42 -0800, george anzinger wrote: > Well, since you asked (thank you), the high-res-timers patch needs to > get the full 64-bit uptime to implement CLOCK_MONOTONIC. > This means that the 64-bit jiffies is used "often" in this code. > Unlike this patch, it keeps the 64-bit rational (i.e. always current)
Well, if you use the get_jiffies64() interface the 64-bit value is always coherent as well, and the direct access to the 32-bit value is monotonic. While the high and low words of the 64-bit jiffies values may be incoherent at times, as long as you always access the 64-bit value with the get_jiffies64() interface it should be OK.
Do you think that doing a 64-bit add-with-carry to memory on each timer interrupt and doing multiple volatile reads is faster than doing a spinlock with an optional 32-bit increment? Do you think there would be a lot of contention on this lock, given that you only need to lock when you need the full 64-bit value?
Cheers, Andreas -- Andreas Dilger http://sourceforge.net/projects/ext2resize/ http://www-mddsp.enel.ucalgary.ca/People/adilger/
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