On Thu, 29 Jan 2015 16:44:43 +0900 Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote: > On Wed, Jan 28, 2015 at 09:30:56AM -0600, Christoph Lameter wrote: > > On Wed, 28 Jan 2015, Joonsoo Kim wrote: > > [...] > > > > The default when no options are specified is to first exhaust the node > > partial objects, then allocate new slabs as long as we have more than > > objects per page left and only then satisfy from cpu local object. I think > > that is satisfactory for the majority of the cases. > > > > The detailed control options were requested at the meeting in Auckland at > > the LCA. I am fine with dropping those if they do not make sense. Makes > > the API and implementation simpler. Jesper, are you ok with this? Yes, I'm okay with dropping the allocation flags. We might want to keep the flag "GFP_SLAB_ARRAY_FULL_COUNT" for allowing allocator to return less-than the requested elements (but I'm not 100% sure). The idea behind this is, if the allocator can "see" that it needs to perform a (relativly) expensive operation, then I would rather want it to return current elements (even if it's less than requested). As this is likely very performance sensitive code using this API. > IMHO, it'd be better to choose a proper way of allocation by slab > itself and not to expose options to API user. We could decide the > best option according to current status of kmem_cache and requested > object number and internal implementation. > > Is there any obvious example these option are needed for user? The use-cases were, if the subsystem/user know about their use-case e.g. 1) needing a large allocation which does not need to be cache hot, 2) needing a smaller (e.g 8-16 elems) allocation that should be cache hot. But, as you argue, I guess it is best to leave this up to the slab implementation as the status of the kmem_cache is only known to the allocator itself. -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer -- 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>