Messages in this thread | | | Date | Tue, 20 Oct 1998 14:50:25 -0500 | From | Mitchell Blank Jr <> | Subject | Re: [patch] jiffies wraparound [Re: 2.1.125 Show stopper list: Draft] |
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Andi Kleen wrote: > > good point. Especially soft-RT-people like the choice of HZ=1000, > > millisec-accuracy scheduling and timers. I remember someone even used > > 10000, to get 100 usec accuracy timers. Even a low-end PC can take HZ=10k. > > That one wraps jiffies every 4 days! > > There is only one problem with it: glibc doesn't know about it and returns > the wrong value to posix conformant programs trying to get it with sysconf(). > Solution: add a readonly sysctl for HZ.
If you're going to do this *please* do PAGE_SIZE at the same time. It suffers from the same problem on architectures where that's variable (m68k being the only one I know of - 8K for sun3, 4K for other things) Right now you need two libc's to solve this problem.
The other posibility would be to create a kernel syscall for sysconf to return kenrel-specific things - there are several other ones. Also we should have a real pathconf which will require a new VFS entry point.
However, having HZ and PAGE_SIZE in sysctl is something that I think we could have in 2.2 still. It's certainly useful to let the user see that info anyway.
-Mitch
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