On Thu, Aug 8, 2013 at 12:25 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > > Whoops -- I read your email too quickly. I haven't tried > MADV_WILLNEED, but I think I tried reading each page to fault them in. > Is there any reason to expect MADV_WILLNEED to do any better? I'll > try to do some new tests to see how well this all works. > > (I imagine that freshly fallocated files are somehow different when > read, since there aren't zeros on the disk backing them until they get > written.) Well, this will teach me to write code based on an old benchmark from memory. It seems that prefaulting for read is okay on Linux 3.9 -- latencytop isn't do_wp_page or ext4* at all, at least not for the last couple minutes on my test box. I wonder if ext4 changed its handling of fallocated extents somewhere between 3.5 and 3.9. In any case, please consider these patches withdrawn for the time being. * With file_update_time stubbed out. I need to dust off my old patches to fix that part. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>