Resending.. There were some email delivery issues. On 9/13/2021 1:27 PM, Dave Hansen wrote: > User Interrupts directly deliver events to user space and are > 10x faster than the closest alternative. Thanks Dave. This is definitely more attention-grabbing than the previous intro. I'll include this next time. One thing to note, the 10x gain is only applicable for User IPIs. For other source of User Interrupts (like kernel-to-user notifications and other external sources), we don't have the data yet. I realized the User IPI data in the cover also needs some clarification. The 10x gain is only seen when the receiver is spinning in User space - waiting for interrupts. If the receiver were to block (wait) in the kernel, the performance would drop as expected. However, User IPI (blocked) would still be 10% faster than Eventfd and 40% faster than signals. Here is the updated table: +---------------------+-------------------------+ | IPC type | Relative Latency | | |(normalized to User IPI) | +---------------------+-------------------------+ | User IPI | 1.0 | | User IPI (blocked) | 8.9 | | Signal | 14.8 | | Eventfd | 9.7 | | Pipe | 16.3 | | Domain | 17.3 | +---------------------+-------------------------+ --Sohil
