On Mon, 2016-04-11 at 21:47 +0200, Jesper Dangaard Brouer wrote: > On Mon, 11 Apr 2016 09:53:54 -0700 > Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote: > > > On Mon, 2016-04-11 at 18:19 +0200, Jesper Dangaard Brouer wrote: > > > > > Drivers also do tricks where they fallback to smaller order pages. E.g. > > > lookup function mlx4_alloc_pages(). I've tried to simulate that > > > function here: > > > https://github.com/netoptimizer/prototype-kernel/blob/91d323fc53/kernel/mm/bench/page_bench01.c#L69 > > > > We use order-0 pages on mlx4 at Google, as order-3 pages are very > > dangerous for some kind of attacks... > > Interesting! > > > An out of order TCP packet can hold an order-3 pages, while claiming to > > use 1.5 KBvia skb->truesize. > > > > order-0 only pages allow the page recycle trick used by Intel driver, > > and we hardly see any page allocations in typical workloads. > > Yes, I looked at the Intel ixgbe drivers page recycle trick. > > It is actually quite cool, but code wise it is a little hard to > follow. I started to look at the variant in i40e, specifically > function i40e_clean_rx_irq_ps() explains it a bit more explicit. > > > > While order-3 pages are 'nice' for friendly datacenter kind of > > traffic, they also are a higher risk on hosts connected to the wild > > Internet. > > > > Maybe I should upstream this patch ;) > > Definitely! > > Does this patch also include a page recycle trick? Else how do you get > around the cost of allocating a single order-0 page? > Yes, we use the page recycle trick. Obviously not on powerpc (or any arch with PAGE_SIZE >= 8192), but definitely on x86. -- 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>