On Thu, May 24, 2012 at 12:00 AM, Paolo Bonzini <pbonz...@redhat.com> wrote:
> Il 23/05/2012 17:14, zwu.ker...@gmail.com ha scritto:
>> From: Zhi Yong Wu <wu...@linux.vnet.ibm.com>
>>
>> Signed-off-by: Zhi Yong Wu <wu...@linux.vnet.ibm.com>
>> ---
>> net/queue.c | 4 ++--
>> net/slirp.c | 7 -------
>> net/tap.c | 2 +-
>> slirp/if.c | 5 -----
>> slirp/libslirp.h | 1 -
>> 5 files changed, 3 insertions(+), 16 deletions(-)
>>
>> diff --git a/net/queue.c b/net/queue.c
>> index 0afd783..d2e57de 100644
>> --- a/net/queue.c
>> +++ b/net/queue.c
>> @@ -176,7 +176,7 @@ ssize_t qemu_net_queue_send(NetQueue *queue,
>> {
>> ssize_t ret;
>>
>> - if (queue->delivering) {
>> + if (queue->delivering || !qemu_can_send_packet(sender)) {
>> return qemu_net_queue_append(queue, sender, flags, data, size,
>> NULL);
>> }
>>
>> @@ -200,7 +200,7 @@ ssize_t qemu_net_queue_send_iov(NetQueue *queue,
>> {
>> ssize_t ret;
>>
>> - if (queue->delivering) {
>> + if (queue->delivering || !qemu_can_send_packet(sender)) {
>> return qemu_net_queue_append_iov(queue, sender, flags, iov, iovcnt,
>> NULL);
>> }
>>
>> diff --git a/net/slirp.c b/net/slirp.c
>> index a6ede2b..248f7ff 100644
>> --- a/net/slirp.c
>> +++ b/net/slirp.c
>> @@ -96,13 +96,6 @@ static void slirp_smb_cleanup(SlirpState *s);
>> static inline void slirp_smb_cleanup(SlirpState *s) { }
>> #endif
>>
>> -int slirp_can_output(void *opaque)
>> -{
>> - SlirpState *s = opaque;
>> -
>> - return qemu_can_send_packet(&s->nc);
>> -}
>> -
>> void slirp_output(void *opaque, const uint8_t *pkt, int pkt_len)
>> {
>> SlirpState *s = opaque;
>> diff --git a/net/tap.c b/net/tap.c
>> index 65f45b8..7b1992b 100644
>> --- a/net/tap.c
>> +++ b/net/tap.c
>> @@ -210,7 +210,7 @@ static void tap_send(void *opaque)
>> if (size == 0) {
>> tap_read_poll(s, 0);
>> }
>> - } while (size > 0 && qemu_can_send_packet(&s->nc));
>> + } while (size > 0);
>
> Can you explain this? Also, have you benchmarked the change to see what
Its code execution flow is like below:
tap_send --> qemu_send_packet_async
->qemu_send_packet_async_with_flags ->qemu_net_queue_send
So it will finally invoke qemu_can_send_packet to determine if it can
send packets. this code change delay this determination.
> effect it has?
No, i have not done benchmark testing. When a lot of packets will go
to the guest from outside and this guest' NIC can_receive return
false, this change will cause CPU to execute some additional codes.
>
> Also, can you explain why you didn't implement this?
Hub can now do its own flow control if it provides its can_recieve.
Why need we add some counts to track in-flight packets? Do you think
that it can speed up the packets delivery? otherwise i think that it
complex the code. To be honest, i prefer current solution. Do you
think of this? :)
>
>>> If they did, hubs could then do their own flow control via can_receive.
>>> When qemu_send_packet returns zero you increment a count of in-flight
>>> packets, and a sent-packet callback would decrement the same count. When the
>>> count is non-zero, can_receive returns false (and vice versa). The sent_cb
>>> also needs to call qemu_flush_queued_packets when the count drop to zero.
>>> With this in place, I think the other TODO about the return value is easily
>>> solved; receive/receive_iov callbacks can simply return immediate success,
>>> and later block further sends.
>
> Paolo
>
>> }
>>
>> int tap_has_ufo(NetClientState *nc)
>> diff --git a/slirp/if.c b/slirp/if.c
>> index 096cf6f..533295d 100644
>> --- a/slirp/if.c
>> +++ b/slirp/if.c
>> @@ -177,11 +177,6 @@ void if_start(Slirp *slirp)
>> }
>>
>> while (ifm_next) {
>> - /* check if we can really output */
>> - if (!slirp_can_output(slirp->opaque)) {
>> - break;
>> - }
>> -
>> ifm = ifm_next;
>> from_batchq = next_from_batchq;
>>
>> diff --git a/slirp/libslirp.h b/slirp/libslirp.h
>> index 77527ad..9b471b5 100644
>> --- a/slirp/libslirp.h
>> +++ b/slirp/libslirp.h
>> @@ -25,7 +25,6 @@ void slirp_select_poll(fd_set *readfds, fd_set *writefds,
>> fd_set *xfds,
>> void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len);
>>
>> /* you must provide the following functions: */
>> -int slirp_can_output(void *opaque);
>> void slirp_output(void *opaque, const uint8_t *pkt, int pkt_len);
>>
>> int slirp_add_hostfwd(Slirp *slirp, int is_udp,
>
--
Regards,
Zhi Yong Wu
