On Wed, Oct 14, 2009 at 7:39 PM, Leonidas . <leonidas137@xxxxxxxxx> wrote: > On Wed, Oct 14, 2009 at 6:56 AM, vinit dhatrak <vinit.dhatrak@xxxxxxxxx> wrote: >> On Wed, Oct 14, 2009 at 4:34 PM, Leonidas . <leonidas137@xxxxxxxxx> wrote: >>> On Wed, Oct 14, 2009 at 3:34 AM, Leonidas . <leonidas137@xxxxxxxxx> wrote: >>>> Hi, >>>> >>>> I am running Ubuntu Jaunty currently, with kernel version 2.6.28 kernel. >>>> I was assuming that, all the kernels above 2.6 will have CONFIG_PREEMPT >>>> =1 by default, but my default kernel does not have it set. >>>> >>>> Is that the norm? I can understand certain use cases which might require >>>> the kernel to be non pre-emptible but even a regular desktop distro does >>>> not have it set? Surprising? >>>> >>>> -Leo. >>>> >>> >>> >>> Even the vmware image which I use for development does not have >>> CONFIG_PREEMPT=1. >>> though it says kernel is SMP. >>> >>> #uname -a >>> >>> Linux ubuntu-vm 2.6.27.2 -generic #1 SMP Thu Aug 28 17:20:02 UTC 2008 >>> i686 GNU/Linux >>> >>> -Leo. >>> >>> -- >>> To unsubscribe from this list: send an email with >>> "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx >>> Please read the FAQ at http://kernelnewbies.org/FAQ >>> >>> >> >> Ok so I can see 3 option for setting preemption model while building kernel, >> >> 1) CONFIG_PREEMPT_NONE 2) CONFIG_PREEMPT_VOLUNTARY (default) >> 3) CONFIG_PREEMPT (might be Ubuntu specific because I can not see this >> in vanila kernel) >> >> >> So by default on Ubuntu (Desktop), CONFIG_PREEMPT_VOLUNTARY is >> selected not CONFIG_PREEMPT >> >> The difference between symbol exported by these 2 kernels is, >> >> 1) Ubuntu (CONFIG_PREEMPT_VOLUNTARY) (You can see some symbols by kvm >> also but you can ignore them) >> >> vinitd@pe-lt271:~$ cat /proc/kallsyms | grep preempt >> c0121550 T preempt_notifier_register >> c0121580 T preempt_notifier_unregister >> c012a350 t check_preempt_curr_idle >> c012ab50 t check_preempt_curr_rt >> c012ac50 t check_preempt_wakeup >> c045a8f0 r __ksymtab_preempt_notifier_unregister >> c045a8f8 r __ksymtab_preempt_notifier_register >> c045ed3c r __kcrctab_preempt_notifier_unregister >> c045ed40 r __kcrctab_preempt_notifier_register >> c0460612 r __kstrtab_preempt_notifier_unregister >> c046062e r __kstrtab_preempt_notifier_register >> c0477824 D preempt_mark_thresh >> f8fc8a68 d kvm_preempt_ops [kvm] >> c0121550 u preempt_notifier_register [kvm] >> c0121580 u preempt_notifier_unregister [kvm] >> f8d46000 t lp_preempt [lp] >> vinitd@pe-lt271:~$ >> >> >> 2) Vanilla kernel (CONFIG_PREEMPT) >> >> # cat /proc/kallsyms | grep preempt >> c00258f4 t svc_preempt >> c00407a8 t check_preempt_curr_rt >> c00407d4 t check_preempt_curr_idle >> c0040ce0 T sub_preempt_count >> c0040d8c T add_preempt_count >> c00441b8 t check_preempt_wakeup >> c0308c84 T preempt_schedule_irq >> c0308d00 T preempt_schedule >> c03b3a70 r __ksymtab_add_preempt_count >> c03b3a78 r __ksymtab_sub_preempt_count >> c03b3a88 r __ksymtab_preempt_schedule >> c03ba5c7 r __kstrtab_add_preempt_count >> c03ba5d9 r __kstrtab_sub_preempt_count >> c03ba5f4 r __kstrtab_preempt_schedule >> # >> >> >> Hope this will help you. >> >> -Vinit >> > > CONFIG_PREEMPT is universal. > > If you look at the definition of preemptible(), it will be clear. > > -Leo. > What do you mean by universal? Do you mean always TRUE? -Vinit -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
