Messages in this thread | | | From | "Albert D. Cahalan" <> | Subject | Re: sysconf (was Re: RLIM_INFINITY inconsistency between archs) | Date | Mon, 31 Jul 2000 02:12:23 -0400 (EDT) |
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Linus Torvalds writes: > On Sat, 29 Jul 2000, Albert D. Cahalan wrote:
>> ARM systems can have HZ be either 100 or 64, because some hardware >> does not support 100. MIPS, Alpha, and ia64 all seem to support more >> than one HZ value. According to you, binaries should not depend on >> what platform they were compiled for. Asking the admin to supply HZ >> is silly when the kernel damn well knows what it is. So there is no >> sane way to even create this "/etc/sysconf" file you propose. > > No. > > You're asking the wrong question. > > There is no sane reason for the OS to expose HZ. We did it for historical > reasons, because it is the easy thing to do. But you have to understand > what the primary objective of an OS is: to create a virtual environment > that is simple and sane to program against. > > The fact that you think you need sysconf() means that the OS is not doing > a good job! > > And that is one of the fundamental arguments against a sysconf() system > call. It is an implicit admission that there is something wrong, and > instead of fixing it you expose some interface that gives whatever random > fixed numbers the kernel was compiled with.
OK, great. Are you ready to fix it? There are existing patches that you have not applied. (they convert for /proc display) Want them now?
This isn't without faults of course. It puts the conversion code in kernel space. That is more kernel bloat that a mere sysconf(). There is also a loss of accuracy due to round-off or truncation, instead of /proc becoming more accurate as HZ is increased.
> And do you not realize that features never get dropped: they just > end up increasing the binary size and icache pressure forever?
Nah, I dropped support for Linux 1.2 and 2.0 already. Nobody even noticed.
> I have yet to hear a _single_ argument that invalidates the "mmap > /proc/sysconf" approach. Your HZ argument does _not_ do it. It's very easy > indeed for an install-script to determine what kind of machine it runs on, > and then write the appropriate value to /etc/sysconf. This is not rocket > science.
Ugh, grepping the boot messages.
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