On 10/16/2012 05:56 AM, Eric Dumazet wrote: > On Tue, 2012-10-16 at 09:35 -0300, Ezequiel Garcia wrote: > >> Now, returning to the fragmentation. The problem with SLAB is that >> its smaller cache available for kmalloced objects is 32 bytes; >> while SLUB allows 8, 16, 24 ... >> >> Perhaps adding smaller caches to SLAB might make sense? >> Is there any strong reason for NOT doing this? > > I would remove small kmalloc-XX caches, as sharing a cache line > is sometime dangerous for performance, because of false sharing. > > They make sense only for very small hosts. That's interesting... It would be good to measure the performance/size tradeoff here. I'm interested in very small systems, and it might be worth the tradeoff, depending on how bad the performance is. Maybe a new config option would be useful (I can hear the groans now... :-) Ezequiel - do you have any measurements of how much memory is wasted by 32-byte kmalloc allocations for smaller objects, in the tests you've been doing? -- Tim ============================= Tim Bird Architecture Group Chair, CE Workgroup of the Linux Foundation Senior Staff Engineer, Sony Network Entertainment ============================= -- 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>