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