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 -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
