On 04/12/2010 01:36 PM, Andrea Arcangeli wrote:
I should make the default selectable at kernel config time, so developers can keep it =always and distro can set it =madvise (trivial to switch to "always" during boot or with kernel command line). Right now it's =always also to give it more testing btw.
That still means the code will not benefit most applications. Surely a more benign default behaviour is possible? For example, instantiating hugepages on pagefault only in VMAs that are significantly larger than a hugepage (say, 16MB or larger?) and not VM_GROWSDOWN (stack starts small). We can still collapse the small pages into a large page if the process starts actually using the memory in the VMA. Memory use is a serious concern for some people, even people who could really benefit from the hugepages. For example, my home desktop system has 12GB RAM, but also runs 3 production virtual machines (kernelnewbies, PSBL, etc) and often has a test virtual machine as well. Not wasting memory is important, since the system is constantly doing disk IO. Any memory that is taken away from the page cache could hurt things. On the other hand, speeding up the virtual machines by 6% could be a big help too... I'd like to think we can find a way to get the best of both worlds. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>