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Kernel: Update E1000 link state using interrupt

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Calls to link_up() in the E1000 driver would read the link state
directly from the hardware on every call. This had negative
performance impact in high throughput situations since link_up()
is called every time an IP packet's route is resolved.

This patch takes inspiration from the RTL8139 network adapter where
the link state is stored in a bool and only updated when the hardware
generates an interrupt related to link state change.

After this change I measured a ~9% increase in TCP Tx throughput
using:
cat /dev/zero | nc <host_IP> <host_port> from the Serenity VM to my
host machine
This commit is contained in:
drblah 2021-12-31 12:56:15 +01:00 • committed by Andreas Kling
parent d7f6635d55
commit b6ba0f9fad
2 changed files with 7 additions and 6 deletions
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3
Kernel/Net/Intel/E1000NetworkAdapter.h
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@ -27,7 +27,7 @@ public:
virtual ~E1000NetworkAdapter() override;
virtual void send_raw(ReadonlyBytes) override;
virtual bool link_up() override;
virtual bool link_up() override { return m_link_up; };
virtual i32 link_speed() override;
virtual bool link_full_duplex() override;
@ -93,6 +93,7 @@ protected:
OwnPtr<Memory::Region> m_mmio_region;
bool m_has_eeprom { false };
bool m_use_mmio { false };
bool m_link_up { false };
EntropySource m_entropy_source;
WaitQueue m_wait_queue;