Messages in this thread Patch in this message | | | Subject | Re: [patch] jiffies wraparound [Re: 2.1.125 Show stopper list: Draft] | From | Andi Kleen <> | Date | 20 Oct 1998 12:40:45 +0200 |
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In article <Pine.LNX.3.96.981020060434.28951I-100000@chiara.csoma.elte.hu>, MOLNAR Ingo <mingo@chiara.csoma.elte.hu> writes: > On Mon, 19 Oct 1998 ralf@uni-koblenz.de wrote:
>> > I guess it depends on your agenda. An OS that has to be rebooted every >> > 490 days isnt a very good embedded system large or small. "Please remember >> > to reboot your building airconditioning control system about next august" ;) >> > >> > View from on high noted, want me to take it off the list ? >> >> Some people are running kernel at a higher HZ which brings them much closer >> to the danger zone.
> 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.
diff -u -r1.60 include/linux/sysctl.h --- include/linux/sysctl.h 1998/05/07 20:48:57 1.60 +++ include/linux/sysctl.h 1998/07/27 14:06:40 @@ -67,7 +67,8 @@ KERN_PPC_HTABRECLAIM, /* turn htab reclaimation on/off on PPC */ KERN_PPC_ZEROPAGED, /* turn idle page zeroing on/off on PPC */ KERN_MODPROBE, - KERN_SG_BIG_BUFF + KERN_SG_BIG_BUFF, + KERN_HZ /* int: Readonly: export HZ to userspace */ }; diff -u -r1.45 kernel/sysctl.c --- kernel/sysctl.c 1998/06/16 04:38:13 1.45 +++ kernel/sysctl.c 1998/07/27 14:06:57 @@ -55,6 +55,8 @@ extern unsigned long htab_reclaim_on, zero_paged_on; #endif +int hzrate = HZ; /* exported readonly */ + extern int pgt_cache_water[]; static int parse_table(int *, int, void *, size_t *, void *, size_t, @@ -184,6 +186,8 @@ {KERN_SG_BIG_BUFF, "sg-big-buff", &sg_big_buff, sizeof (int), 0444, NULL, &proc_dointvec}, #endif + {KERN_HZ, "clock-rate", &hzrate, sizeof(int), 0444, NULL, + &proc_dointvec}, {0} };
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