On Thu, 23 Aug 2007, Luka Napotnik wrote: > Hello. > > I'm new to kernel development and have some questions. > > 1. Why can't I divide with regular casting to double ((double)a / > (double)b)? It gives me strange errors when compiling: > > WARNING: "__divdf3" [/root....] undefined! > WARNING: "__addf3" [/root/...] undefined! > WARNING: "__floatsidf" [/root/...] undefined! > > And if I compile with normal integers, I get zero as the result. > > 2. I'm trying to get the percentage of CPU used for a certain > task_struct and figured the following formula: > > (task->utime + task->stime) / jiffies > > Before calculating I convert all the variables to jiffies. Is this correct? > > Please help. > > Greets, > Lukla
Floating point operations are not allowed in the kernel. Often, when you think you are simply creating a constant, the compiler generates runtime code so you have to watch out for that as well. You can use "long long" for high precision math if necessary. Cheers, Dick Johnson Penguin : Linux version 2.6.22.1 on an i686 machine (5588.30 BogoMips). My book : http://www.AbominableFirebug.com/ _ **************************************************************** The information transmitted in this message is confidential and may be privileged. Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited. If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to [EMAIL PROTECTED] - and destroy all copies of this information, including any attachments, without reading or disclosing them. Thank you. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
