Can's Awesome Weblog

Receive Livelock

Travis got a new CPU last week and just sent me a large file over AIM. This almost sent my computer into Receive LiveLock. Receive Livelock means that user programs are not making any progress, and packets are being dropped due to the large number of interrupts when the computer is receiving large network loads. More about this can be found in the original paper Eliminating Receive Livelock in an Interrupt-Driven Kernel by Mogul and Ramakrishnan. Though my computer was still making progress, on the file transfer, user programs were making no progress. While you might think that modern schedulers would avoid this problem, it is caused by receiving interrupts, which have priority, and are totally independent of the scheduler. Though buying a faster CPU would eliminate this problem, I think OS vendors should start implementing this feature.