On Thu, Sep 11, 2014 at 5:53 PM, Miles MH Chen <orca.chen@xxxxxxxxx> wrote: > Not exactly, vmalloc'ed addresses can generate page faults. > > vmalloc'ed page entries live in kernel master page table, not in > > every process' page table. When a vmalloc page fault occurs, > > kernel simply copy the page table entry from master page table to > > the current process' page table and fix the page fault. > > MH Thanks, I was under wrong impression that the difference between page allocated in kmalloc vs. vmalloc is in PTE mapping. > > On Thu, Sep 11, 2014 at 8:03 PM, Leon Romanovsky <leon@xxxxxxx> wrote: >> >> On Wed, Sep 10, 2014 at 5:52 PM, Manavendra Nath Manav >> <mnm.kernel@xxxxxxxxx> wrote: >> > >> > On 10-Sep-2014 6:24 pm, <Valdis.Kletnieks@xxxxxx> wrote: >> >> >> >> On Wed, 10 Sep 2014 14:45:23 +0530, Manavendra Nath Manav said: >> >> >> >> > But if the total RAM is limited (less than 896MB LOWMEM), for example >> >> > as >> >> > in >> >> > embedded devices how the kernel code be kept in RAM all the time. Am >> >> > I >> >> > correct to assume that the kernel pre-fetches all pages when entering >> >> > kernel mode from user mode? >> >> >> >> No, kernel code is loaded by your boot loader, and *it stays there*. >> >> Similarly, >> >> if you modprobe something, the kernel allocates the page, loads the >> >> code, >> >> and leaves it there. >> >> >> >> Particularly in embedded devices, where you know all the modules the >> >> kernel may >> >> need, it's common to just create a kernel with everything built in, no >> >> module >> >> support, and when the system boots, it loads into memory and never >> >> moves >> >> again. >> >> >> > >> > Linux kernel memory is not page-able, but memory allocated through >> > vmalloc >> > can still cause page fault. How device drivers using vmalloc handle >> > this? >> Pages allocated via vmalloc call won't generate page-faults. >> >> > >> > >> > _______________________________________________ >> > Kernelnewbies mailing list >> > Kernelnewbies@xxxxxxxxxxxxxxxxx >> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> > >> >> >> >> -- >> Leon Romanovsky | Independent Linux Consultant >> www.leon.nu | leon@xxxxxxx >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies@xxxxxxxxxxxxxxxxx >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > -- Leon Romanovsky | Independent Linux Consultant www.leon.nu | leon@xxxxxxx _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
