On 7/13/05, srinivas bakki <srinivas.bakki@xxxxxxxxx> wrote: > > The only scenario I can think, when two or more processes share VMA of > > text region (pay attention, you are asking about VMA, not the page or > > page frame) are in multi threading. Since they execute same code (in > > most cases, new thread are created with clone() using CLONE_VM), it > > makes sense to share the text region for efficiency. > > Do you mean the page tables are shared ? This means they have the > same page global directory. How is this accomplished ? > Page tables are not owned by any process or thread. They are owned by kernel in general and any request for mapping the virtual memory to physical memroy, needs page tables (actually if the translation is not found in TLB cache)... so no process actually owns the page tables. They are just global data sturctures. A VMA structure contains a range of virtual addresses which are accessible (readable/writable etc) by this process. It has nothing to do with page tables. So VMA can not be shared even in clone(), rather it is copied into other process's task_struct. So with clone() you will have two copies of same VMA values inside both the processes. I think VMA can never be shared (single instance shared by both processes). Please correct me if my understanding is wrong. HTH Ketan -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
