On Fri, Apr 05, 2013 at 02:01:11PM +0400, Glauber Costa wrote: > Right now, allocation for page_cgroup is a bit complicated, dependent on > a variety of system conditions: > > For flat memory, we are likely to need quite big pages, so the page > allocator won't cut. We are forced to init flatmem mappings very early, > because if we run after the page allocator is in place those allocations > will be denied. Flatmem mappings thus resort to the bootmem allocator. > > We can fix this by using vmalloc for flatmem mappings. However, we now > have the situation in which flatmem mapping allocate using vmalloc, but > sparsemem may or may not allocate with vmalloc. It will try the > page_allocator first, and retry vmalloc if it fails. Vmalloc space is a precious resource on 32-bit systems and harder on the TLB than the identity mapping. It's a last resort thing for when you need an unusually large chunk of contiguously addressable memory during runtime, like loading a module, buffers shared with userspace etc.. But here we know, during boot time, the exact amount of memory we need for the page_cgroup array. Code cleanup is not a good reason to use vmalloc in this case, IMO. -- 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>