On 08/07/2013 06:40 AM, Jan Kara wrote: > One question before I look at the patches: Why don't you use fallocate() > in your application? The functionality you require seems to be pretty > similar to it - writing to an already allocated block is usually quick. One problem I've seen is that it still costs you a fault per-page to get the PTEs in to a state where you can write to the memory. MADV_WILLNEED will do readahead to get the page cache filled, but it still leaves the pages unmapped. Those faults get expensive when you're trying to do a couple hundred million of them all at once. -- 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>