13/07/2018 10:31, Hunt, David: > Hi Thomas, > > On 12/7/2018 8:09 PM, Thomas Monjalon wrote: > > 26/06/2018 11:23, David Hunt: > >> This patch set adds the capability to do out-of-band power > >> monitoring on a system. It uses a thread to monitor the branch > >> counters in the targeted cores, and calculates the branch ratio > >> if the running code. > >> > >> If the branch ratop is low (0.01), then > >> the code is most likely running in a tight poll loop and doing > >> nothing, i.e. receiving no packets. In this case we scale down > >> the frequency of that core. > >> > >> If the branch ratio is higher (>0.01), then it is likely that > >> the code is receiving and processing packets. In this case, we > >> scale up the frequency of that core. > >> > >> The cpu counters are read via /dev/cpu/x/msr, so requires the > >> msr kernel module to be loaded. Because this method is used, > >> the patch set is implemented with one file for x86 systems, and > >> another for non-x86 systems, with conditional compilation in > >> the Makefile. The non-x86 functions are stubs, and do not > >> currently implement any functionality. > >> > >> The vm_power_manager app has been modified to take a new parameter > >> --core-list or -l > >> which takes a list of cores in a comma-separated list format, > >> e.g. 1,3,5-7,9, which resolvest to a core list of 1,3,5,6,7,9 > >> These cores will then be enabled for oob monitoring. When the > >> OOB monitoring thread starts, it reads the branch hits/miss > >> counters of each monitored core, and scales up/down accordingly. > > It looks to be a feature which could be integrated in DPDK libs. > > Why choosing to implement it fully in an example? > > I needed to set up a thread that looped tightly (~100uS interval) and > run it on it's > own core. From what I have seen in other cases, it is usually the > application that > allocates cores and decides what to run on them. I did think about putting > some of it in a library, but for this case I thought it made more sense > to keep > it purely as a sample app.
I feel some code deserves to be in a library. For instance, having different implementations per CPU is a good reason to make a library.
