Greetings, everyone, I'm trying to save some data block from a memory mapped device into a file - real fast, i.e., without any copying.
My approach so far was to get a pointer to the io memory via mmap-ing /dev/mem, and then writing this pointer to a file (in user space). This works, if I don't use O_DIRECT, but this is slow of course. Using O_DIRECT, write returns EFAULT (bad address). Coyping the data to a user-space buffer and then writing with O_DIRECT works, though. I tracked this down to __get_user_pages in mm/memory.c where IO pages are refused. And this is as deep as my current knowledge allows me to go into the kernel. I don't understand why IO pointers are not allowed. Ultra-Fast disk IO is a requirement for our project, so any copying in between is not an option. Any hint is appreciated. Stefan _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
