From mboxrd@z Thu Jan 1 00:00:00 1970 From: leon@leon.nu (Leon Romanovsky) Date: Thu, 11 Sep 2014 15:03:04 +0300 Subject: Page fault in kernel code In-Reply-To: References: <4E5779AD88B2F040B8A7E83ECF544D1A55B65C@SJCPEX01CL02.citrite.net> <35026.1410353642@turing-police.cc.vt.edu> Message-ID: To: kernelnewbies@lists.kernelnewbies.org List-Id: kernelnewbies.lists.kernelnewbies.org On Wed, Sep 10, 2014 at 5:52 PM, Manavendra Nath Manav wrote: > > On 10-Sep-2014 6:24 pm, 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 at kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > -- Leon Romanovsky | Independent Linux Consultant www.leon.nu | leon at leon.nu