On Thu, 2009-01-22 at 16:36 +0800, Zhang, Yanmin wrote: > On Wed, 2009-01-21 at 18:58 -0500, Christoph Lameter wrote: > > On Tue, 20 Jan 2009, Zhang, Yanmin wrote: > > > > > kmem_cache skbuff_head_cache's object size is just 256, so it shares the kmem_cache > > > with :0000256. Their order is 1 which means every slab consists of 2 physical pages. > > > > That order can be changed. Try specifying slub_max_order=0 on the kernel > > command line to force an order 0 alloc. > I tried slub_max_order=0 and there is no improvement on this UDP-U-4k issue. > Both get_page_from_freelist and __free_pages_ok's cpu time are still very high. > > I checked my instrumentation in kernel and found it's caused by large object allocation/free > whose size is more than PAGE_SIZE. Here its order is 1. > > The right free callchain is __kfree_skb => skb_release_all => skb_release_data. > > So this case isn't the issue that batch of allocation/free might erase partial page > functionality. So is this the kfree(skb->head) in skb_release_data() or the put_page() calls in the same function in a loop? If it's the former, with big enough size passed to __alloc_skb(), the networking code might be taking a hit from the SLUB page allocator pass-through. Pekka -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
