You're in a dangerous zone where the computer science terms and common-sense terms don't quite overlap.
Real-time drivers can indeed improve the latency bounds of the system, at a throughput (and sometimes a minimum latency) cost - in the case of Linux, however, most drivers are as tight as possible, and it's the core code (e.g. the networking stack, not the NIC drivers) that needs work.
Given that you're being non-specific ("performance" as against throughput or latency), I suspect you've been thinking that the RT kernel options improve everything; if they did, they wouldn't be options. What they do is reduce the maximum latency of any kernel operation, at the expense of slight reductions in throughput here and there; they're not worried about minimum latency, as it's possible (given a fixed maximum latency) to compensate for returns that are too quick.
It's been a long time since I benchmarked the RT kernel, but when I last did, using gigabit ethernet and a custom app, I measured peak latencies dropping from 600 milliseconds to around 50 milliseconds, but throughput dropped from 400 megabits/second to 300 megabits/second. Worth thinking about, anyway.
Be careful with language here
You're in a dangerous zone where the computer science terms and common-sense terms don't quite overlap.
Real-time drivers can indeed improve the latency bounds of the system, at a throughput (and sometimes a minimum latency) cost - in the case of Linux, however, most drivers are as tight as possible, and it's the core code (e.g. the networking stack, not the NIC drivers) that needs work.
Given that you're being non-specific ("performance" as against throughput or latency), I suspect you've been thinking that the RT kernel options improve everything; if they did, they wouldn't be options. What they do is reduce the maximum latency of any kernel operation, at the expense of slight reductions in throughput here and there; they're not worried about minimum latency, as it's possible (given a fixed maximum latency) to compensate for returns that are too quick.
It's been a long time since I benchmarked the RT kernel, but when I last did, using gigabit ethernet and a custom app, I measured peak latencies dropping from 600 milliseconds to around 50 milliseconds, but throughput dropped from 400 megabits/second to 300 megabits/second. Worth thinking about, anyway.