Messages in this thread | | | Date | Wed, 04 Apr 2007 07:09:32 +0200 | From | Eric Dumazet <> | Subject | Re: getting processor numbers |
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H. Peter Anvin a écrit : > Jeremy Fitzhardinge wrote: >> H. Peter Anvin wrote: >>> Sounds like it would need a device which can be waited upon for changes. >> >> A vdso-like shared page could have a futex in it. > > Yes, but a futex couldn't be waited upon with a bunch of other things as > part of a poll or a select. The cost of reading the information is > minimal. >
There is one thing that always worried me.
Intel & AMD manuals make clear that mixing data and program in the same page is bad for performance.
In particular, x86_64 vsyscall put jiffies and other vsyscall_gtod_data_t right in the midle of code. That is certainly not wise.
A probably sane implementation should use two pages, one for code, one for data.
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