Messages in this thread | | | Subject | Re: finding out the value of HZ from userspace | From | Arjan van de Ven <> | Date | Sat, 13 Mar 2004 23:32:39 +0100 |
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On Sat, 2004-03-13 at 23:14, Micha Feigin wrote: > On Sat, Mar 13, 2004 at 08:38:52PM +0100, Arjan van de Ven wrote: > > On Sat, Mar 13, 2004 at 11:34:37AM -0800, John Reiser wrote: > > > Arjan van de Ven wrote: > > > >On Thu, 2004-03-11 at 15:17, Micha Feigin wrote: > > > > > > > >>Is it possible to find out what the kernel's notion of HZ is from user > > > >>space? > > > >>It seem to change from system to system and between 2.4 (100 on i386) > > > >>to 2.6 (1000 on i386). > > > > > > > > > > > >if you can see 1000 from userspace that is a bad kernel bug; can you say > > > >where you find something in units of 1000 ? > > > > > > create_elf_tables() in fs/binfmt_elf.c tells every ELF execve(): > > > NEW_AUX_ENT(AT_CLKTCK, CLOCKS_PER_SEC); > > > which can be found by crawling through the stack above the pointer > > > to the last environment variable. > > > > Ugh that should say 100 on x86.... > > but.. > > param.h:# define USER_HZ 100 /* .. some user interfaces are in "ticks" */ > > param.h:# define CLOCKS_PER_SEC (USER_HZ) /* like times() */ > > ..... > > that looks like 100 to me. > > > > When dealing with bdflush and a few other interfaces the values need to > be in jiffies which requires knowledge of the kernels notion of HZ not > userspace.
Wrong. Any such interface is supposed to convert automatically. Any interface you can find that doesn't should be reported as a serious bug!
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