On Tue, Aug 28, 2018 at 11:11:02AM +0800, Jin, Yao wrote:

Hi,

The upstream kernel has supported IIO free-running counters on Skylake
server. As of Skylake Server, there are a number of free running counters in
each IIO Box that collect counts of per-box IO clocks and per-port
Input/Output x BW/Utilization.

There are three types of IIO free-running counters on Skylake server:

1. IO CLOCKS counter: a clock of IIO box.

2. BANDWIDTH counters: count inbound(PCIe->CPU)/outbound(CPU->PCIe)
bandwidth.

3. UTILIZATION counters: count input/output utilization.

With these IIO free-running counters, we can get good observation for IIO
traffic on Skylake server. For example, we can see the IIO inbound bandwidth
(PCIe->CPU).

root@skx /sys/devices# perf stat -a -e
uncore_iio_free_running_2/bw_in_port0/
^C
 Performance counter stats for 'system wide':

            153.19 MiB  uncore_iio_free_running_2/bw_in_port0/

       8.037701069 seconds time elapsed

I propose to backport the patches which support IIO free-running counters to
4.14 stable kernel.

perf/x86/intel/uncore: Introduce customized event_read() for client IMC
uncore
2da331465f44f9618abe8837d1a68405d550b66e

perf/x86/intel/uncore: Add new data structures for free running counters
927b2deb067b8b4753fc09c7a42092f43fc0c1f6

perf/x86/intel/uncore: Add infrastructure for free running counters
0e0162dfcd1fbe4c711ee86f24f966c318999603

perf/x86/intel/uncore: Support IIO free-running counters on SKX
0f519f0352e37e7d71bdce5559517c74a35f6e33

perf/x86/intel/uncore: Expose uncore_pmu_event*() functions
5a6c9d94e9ed7410142bc6fcb638a4db1895aa0c

perf/x86/intel/uncore: Clean up client IMC uncore
9aae1780e7e81e54edfb70ba33ead5b0b48be009

Where in the stable kernel rules does it say that these types of patches
are ok to be backported?

Why not just use a newer kernel release if you want to use these new
features?  What is preventing these users from using 4.18 or newer?

thanks,

greg k-h