OK, here's the real reason I was digging around for exactly which fields in 'struct page' slub uses. SLUB depends on a 16-byte cmpxchg for an optimization. For the purposes of this series, I'm assuming that it is a very important optimization that we desperately need to keep around. In order to get guaranteed 16-byte alignment (required by the hardware on x86), 'struct page' is padded out from 56 to 64 bytes. Those 8-bytes matter. We've gone to great lengths to keep 'struct page' small in the past. It's a shame that we bloat it now just for alignment reasons when we have extra space. These patches attempt _internal_ alignment instead of external alignment for slub. I also got a bug report from some folks running a large database benchmark. Their old kernel uses slab and their new one uses slub. They were swapping and couldn't figure out why. It turned out to be the 2GB of RAM that the slub padding wastes on their system. On my box, that 2GB cost about $200 to populate back when we bought it. I want my $200 back. This is compile tested and lightly runtime tested. I'm curious what people think of it before we push it futher. This is on top of my previous patch to create a 'struct slab_page', but doesn't really rely on it. It could easily be done independently. -- 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>