On Mon, 16 May 2016 15:51:48 +0800 Jason Wang <jasow...@redhat.com> wrote:
> On 2016年05月16日 11:56, Eric Dumazet wrote: > > On Mon, 2016-05-16 at 09:17 +0800, Jason Wang wrote: > >> We used to queue tx packets in sk_receive_queue, this is less > >> efficient since it requires spinlocks to synchronize between producer > >> and consumer. > > ... > > > >> struct tun_struct *detached; > >> + /* reader lock */ > >> + spinlock_t rlock; > >> + unsigned long tail; > >> + struct tun_desc tx_descs[TUN_RING_SIZE]; > >> + /* writer lock */ > >> + spinlock_t wlock; > >> + unsigned long head; > >> }; > >> > > Ok, we had these kind of ideas floating around for many other cases, > > like qdisc, UDP or af_packet sockets... > > > > I believe we should have a common set of helpers, not hidden in > > drivers/net/tun.c but in net/core/skb_ring.c or something, with more > > flexibility (like the number of slots) > > > > Yes, this sounds good. I agree. It is sad to see everybody is implementing the same thing, open coding an array/circular based ring buffer. This kind of code is hard to maintain and get right with barriers etc. We can achieve the same performance with a generic implementation, by inlining the help function calls. I implemented an array based Lock-Free/cmpxchg based queue, that you could be inspired by, see: https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/include/linux/alf_queue.h The main idea behind my implementation is bulking, to amortize the locked cmpxchg operation. You might not need it now, but I expect we need it in the future. You cannot use my alf_queue directly as your "struct tun_desc" is larger than one-pointer (which the alf_queue works with). But it should be possible to extend to handle larger "objects". Maybe Steven Rostedt have an even better ring queue implementation already avail in the kernel? -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer
