On Mon, 27 Oct 2014, Joonsoo Kim wrote: > > One other aspect of this patchset is that it reduces the cache footprint > > of the alloc and free functions. This typically results in a performance > > increase for the allocator. If we can avoid the page_address() and > > virt_to_head_page() stuff that is required because we drop the ->page > > field in a sufficient number of places then this may be a benefit that > > goes beyond the RT and CONFIG_PREEMPT case. > > Yeah... if we can avoid those function calls, it would be good. One trick that may be possible is to have an address mask for the page_address. If a pointer satisfies the mask requuirements then its on the right page and we do not need to do virt_to_head_page. > But, current struct kmem_cache_cpu occupies just 32 bytes on 64 bits > machine, and, that means just 1 cacheline. Reducing size of struct may have > no remarkable performance benefit in this case. Hmmm... If we also drop the partial field then a 64 byte cacheline would fit kmem_cache_cpu structs from 4 caches. If we place them correctly then the frequently used caches could avoid fetching up to 3 cachelines. You are right just dropping ->page wont do anything since the kmem_cache_cpu struct is aligned to a double word boundary. -- 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>