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LwIP: manage Nic pbufs with a slab allocator

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LwIP skips a packet copy by wrapping Nic stream buffer regions in LwIP
pbuf objects. Move from a fixed size array to a potentially unbounded
slab allocator for managing this buffer metadata.

Ref #2335
This commit is contained in:
Emery Hemingway 2018-08-08 15:21:13 +02:00 committed by Christian Helmuth
parent 4bb5046e1f
commit 22ef3ed474
1 changed files with 31 additions and 41 deletions
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72
repos/libports/include/lwip/nic_netif.h
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@ -47,21 +47,27 @@ extern "C" {
extern "C" {
/**
* Metadata for packet backed pbufs
*/
struct nic_netif_pbuf
{
struct pbuf_custom p { };
Nic_netif *netif = nullptr;
Nic::Packet_descriptor packet { };
};
static void nic_netif_pbuf_free(pbuf *p);
static err_t nic_netif_init(struct netif *netif);
static err_t nic_netif_linkoutput(struct netif *netif, struct pbuf *p);
static void nic_netif_status_callback(struct netif *netif);
}
/**
* Metadata for packet backed pbufs
*/
struct Nic_netif_pbuf
{
struct pbuf_custom p { };
Nic_netif &netif;
Nic::Packet_descriptor packet;
Nic_netif_pbuf(Nic_netif &nic, Nic::Packet_descriptor &pkt)
: netif(nic), packet(pkt)
{
p.custom_free_function = nic_netif_pbuf_free;
}
};
}
@ -70,15 +76,11 @@ class Lwip::Nic_netif
private:
enum {
PBUFS_QUEUE_SIZE = 128,
NIC_BUF_SIZE =
Nic::Packet_allocator::DEFAULT_PACKET_SIZE *
PBUFS_QUEUE_SIZE
PACKET_SIZE = Nic::Packet_allocator::DEFAULT_PACKET_SIZE,
BUF_SIZE = 128 * PACKET_SIZE,
};
nic_netif_pbuf _pbufs[PBUFS_QUEUE_SIZE];
unsigned _pbufs_next = 0;
unsigned _alloced = 0;
Genode::Tslab<struct Nic_netif_pbuf, 128> _pbuf_alloc;
Nic::Packet_allocator _nic_tx_alloc;
Nic::Connection _nic;
@ -94,14 +96,14 @@ class Lwip::Nic_netif
public:
void free_pbuf(nic_netif_pbuf &pbuf)
void free_pbuf(Nic_netif_pbuf &pbuf)
{
if (!_nic.rx()->ready_to_ack()) {
Genode::error("Nic rx acknowledgement queue congested, blocking to free pbuf");
}
_nic.rx()->acknowledge_packet(pbuf.packet);
pbuf.packet = Nic::Packet_descriptor();
destroy(_pbuf_alloc, &pbuf);
}
@ -129,30 +131,17 @@ class Lwip::Nic_netif
auto &rx = *_nic.rx();
while (rx.packet_avail() && rx.ready_to_ack()) {
unsigned const initial_index = _pbufs_next;
while (_pbufs[_pbufs_next].packet.size()) {
_pbufs_next = (_pbufs_next+1) % PBUFS_QUEUE_SIZE;
if (_pbufs_next == initial_index) {
/* internal pbuf queue congested */
return;
}
}
Nic::Packet_descriptor packet = rx.get_packet();
Nic::Packet_descriptor const packet = rx.get_packet();
nic_netif_pbuf &nic_pbuf = _pbufs[_pbufs_next];
_pbufs_next = (_pbufs_next+1) % PBUFS_QUEUE_SIZE;
nic_pbuf.p.custom_free_function = nic_netif_pbuf_free;
nic_pbuf.netif = this;
nic_pbuf.packet = packet;
Nic_netif_pbuf *nic_pbuf = new (_pbuf_alloc)
Nic_netif_pbuf(*this, packet);
pbuf* p = pbuf_alloced_custom(
PBUF_RAW,
packet.size(),
PBUF_REF,
&nic_pbuf.p,
&nic_pbuf->p,
rx.packet_content(packet),
packet.size());
LINK_STATS_INC(link.recv);
@ -217,9 +206,10 @@ class Lwip::Nic_netif
Genode::Allocator &alloc,
Genode::Xml_node config)
:
_nic_tx_alloc(&alloc),
_nic(env, &_nic_tx_alloc, NIC_BUF_SIZE, NIC_BUF_SIZE,
config.attribute_value("label", Genode::String<160>("lwip")).string()),
_pbuf_alloc(alloc), _nic_tx_alloc(&alloc),
_nic(env, &_nic_tx_alloc,
BUF_SIZE, BUF_SIZE,
config.attribute_value("label", Genode::String<160>("lwip")).string()),
_link_state_handler(env.ep(), *this, &Nic_netif::handle_link_state),
_rx_packet_handler( env.ep(), *this, &Nic_netif::handle_rx_packets)
{
@ -359,8 +349,8 @@ namespace Lwip {
*/
static void nic_netif_pbuf_free(pbuf *p)
{
nic_netif_pbuf *nic_pbuf = (nic_netif_pbuf*)(p);
nic_pbuf->netif->free_pbuf(*nic_pbuf);
Nic_netif_pbuf *nic_pbuf = reinterpret_cast<Nic_netif_pbuf*>(p);
nic_pbuf->netif.free_pbuf(*nic_pbuf);
}