On Fri, Nov 03, 2023 at 10:11:08AM +0000, Konstantin Ananyev wrote: > > > Hi all, > > > > looking to start a discussion and get some input here. > > > > There are a number of our examples in DPDK which still track core usage via > > a 64-bit bitmask, and, as such, cannot run on cores between 64 and > > RTE_MAX_LCORE. Two examples I have recently come across with this issue are > > "eventdev_pipeline" and "qos_sched", but I am sure there are others. The > > former is a good example (or bad example depending on your viewpoint) of > > this as it takes multiple coremask parameters - for RX cores, for TX cores, > > for worker cores and optionally for scheduler cores. > > > > Now, the simple solution to this is to just expand the 64-bit bitmask to > > 128 bit or more, but I think that is just making things harder for the > > user, since dealing with long bitmasks is very awkward and unwieldy. Better > > instead to convert all examples using coremasks to using core lists > > instead. > > > > First step should be to take our EAL corelist processing code and refactor > > it into a function that can be made public, so that it can be used by all > > apps for parsing core lists. Simple enough! > > > > The next part I'm looking for input on is - how do we switch the apps from > > coremasks to core lists? Some options: > > > > 1. Add in new commandline parameters for each app to work with core lists. > > This is what we did in the past with EAL, by adding -l as a replacement > > for -c. The advantage is that we maintain backward compatibility, but the > > downside is that it becomes hard to find new suitable letter options for > > the core lists. Taking eventdev_pipeline again, we would need "new" > > options for "-r", "-t", "-w" and "-s" parameters. Using the capitalized > > versions of these would be a simple alternative, but "-W" is already used > > as an app parameter so we can't do that. > > > > 2. Just break backward compatibility and switch the apps to taking > > core lists instead of masks. Advantage is that it gives us the cleanest > > solution, but the downside is that and testing done using these examples, > > or any users who may have run them in the past, get different behaviour. > > > As it is for examples, I also don't see any issue with converting to > core-list. > Said that, I suppose we still want to keep EAL '-c' (coremask) parameter, > right? > If so, then it might be plausible to consider making the code that handles it > to work with really-long ones (up to 1K, or whatever is our current CPU_SET > limit).
I believe the EAL coremask parsing already supports >64 lcores, and works with arbitrary lengths up to RTE_MAX_LCORE, so I think we are ok here. It parses the coremask char-by-char (backwards) as a string, rather than trying to convert it using atoi-type functions[1]. /Bruce [1] http://git.dpdk.org/dpdk/tree/lib/eal/common/eal_common_options.c#n777
