On Wed, Aug 24, 2016 at 11:01:43PM -0500, Christoph Lameter wrote: > On Wed, 24 Aug 2016, Mel Gorman wrote: > > If/when I get back to the page allocator, the priority would be a bulk > > API for faster allocs of batches of order-0 pages instead of allocating > > a large page and splitting. > > > > OMG. Do we really want to continue this? There are billions of Linux > devices out there that require a reboot at least once a week. This is now > standard with certain Android phones. In our company we reboot all > machines every week because fragmentation degrades performance > significantly. We need to finally face up to it and deal with the issue > instead of continuing to produce more half ass-ed solutions. > Flipping the lid aside, there will always be a need for fast management of 4K pages. The primary use case is networking that sometimes uses high-order pages to avoid allocator overhead and amortise DMA setup. Userspace-mapped pages will always be 4K although fault-around may benefit from bulk allocating the pages. That is relatively low hanging fruit that would take a few weeks given a free schedule. Dirty tracking of pages on a 4K boundary will always be required to avoid IO multiplier effects that cannot be side-stepped by increasing the fundamental unit of allocation. Batching of tree_lock during reclaim for large files and swapping is also relatively low hanging fruit that also is doable in a week or two. A high-order per-cpu cache for SLUB to reduce zone->lock contention is also relatively low hanging fruit with the caveat it makes per_cpu_pages larger than a cache line. If you want to rework the VM to use a larger fundamental unit, track sub-units where required and deal with the internal fragmentation issues then by all means go ahead and deal with it. -- Mel Gorman SUSE Labs -- 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>