On Thu, 8 Mar 2007, Carsten Otte wrote: > On 3/8/07, Martin Drab <[EMAIL PROTECTED]> wrote: > > > > The thing is that I'd like to prevent kernel to swap these pages out, > > because then I may loose some data when they are not available in time > > for the next round. > > One think you could do is grab a reference to the pages upfront.
I'm not really sure what exactly do you mean by "grab a reference upfront"? > When you stop pushing data out to the userspace, or at least when the > file is released, you need to drop that reference again. Or do you mean reference like with the get_page()? Sure, I do a get_page() in the nopage() handler for each page before it is passed to the user-space. That's OK, there is no problem. Problem seems to be in the PG_reserved bit set when the pages are unmapped from the userspace, i.e. when the application calls munmap(2). > You could even do a kmap_atomic(), which would give you a kernel space > mapping. That way, you avoid copy_to_user for that data. If I understand kmap_atomic() right, then it is not really what I need in this case. The kmap() just returns a virtual address (logical address in this case, since the pages are not in high memory) for a page. The kmap_atomic() does the same but disables preemption first, so all processing with the page needs to be atomic, which in this case can not be guaranteed. Or do I get it wrong? I'm not really a kernel's memory management guru, so maybe I just don't get it. ;-) But thanks anyway. Martin - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
