On Mon, Apr 07, 2025 at 08:14:50AM -0700, Stephen Hemminger wrote: > On Mon, 7 Apr 2025 12:15:13 +0200 > Morten Brørup <m...@smartsharesystems.com> wrote: > > > > From: Bruce Richardson [mailto:bruce.richard...@intel.com] > > > Sent: Monday, 7 April 2025 11.49 > > > > > > On Mon, Apr 07, 2025 at 09:04:05AM +0200, David Marchand wrote: > > > > Hello Bruce, > > > > > > > > On Tue, Apr 1, 2025 at 4:08 PM Bruce Richardson > > > > <bruce.richard...@intel.com> wrote: > > > > > > > > > > On Mon, Mar 24, 2025 at 05:30:26PM +0000, Bruce Richardson wrote: > > > > > > Traditionally, DPDK has had a direct mapping of internal lcore- > > > ids, to > > > > > > the actual core numbers in use. With higher core count servers > > > becoming > > > > > > more prevalent the issue becomes one of increasing memory > > > footprint when > > > > > > using such a scheme, due to the need to have all arrays > > > dimensioned for > > > > > > all cores on the system, whether or not those cores are in use by > > > the > > > > > > app. > > > > > > > > > > > > Therefore, the decision was made in the past to not expand the > > > > > > build-time RTE_MAX_LCORE value beyond 128. Instead, it was > > > recommended > > > > > > that users use the "--lcores" EAL parameter to take the high- > > > numbered > > > > > > cores they wish to use and map them to lcore-ids within the 0 - > > > 128 > > > > > > range. While this works, this is a little clunky as it means that > > > > > > instead of just passing, for example, "-l 130-139", the user must > > > > > > instead pass "--lcores 0@130,1@131,2@132,3@133,...." > > > > > > > > > > > > This patchset attempts to simplify the situation by adding a new > > > flag to > > > > > > do this mapping automatically. To use cores 130-139 and map them > > > to ids > > > > > > 0-9 internally, the EAL args now become: "-l 130-139 --map-lcore- > > > ids", > > > > > > or using the shorter "-M" version of the flag: "-Ml 130-139". > > > > > > > > > > > > Adding this new parameter required some rework of the existing > > > arg > > > > > > parsing code, because in current DPDK the args are parsed and > > > checked in > > > > > > the order they appear on the commandline. This means that using > > > the > > > > > > example above, the core parameter 130-139 will be rejected > > > immediately > > > > > > before the "map-lcore-ids" parameter is seen. To work around > > > this, the > > > > > > core (and service core) parameters are not parsed when seen, > > > instead > > > > > > they are only saved off and parsed after all arguments are > > > parsed. The > > > > > > "-l" and "-c" parameters are converted into "--lcores" arguments, > > > so all > > > > > > assigning of lcore ids is done there in all cases. > > > > > > > > > > > > RFC->v2: > > > > > > * converted printf to DEBUG log > > > > > > * added "-M" as shorter version of flag > > > > > > * added documentation > > > > > > * renamed internal API that was changed to avoid any potential > > > hidden > > > > > > runtime issues. > > > > > > > > > > > > Bruce Richardson (3): > > > > > > eal: centralize core parameter parsing > > > > > > eal: convert core masks and lists to core sets > > > > > > eal: allow automatic mapping of high lcore ids > > > > > > > > > > > Ping for review. > > > > > > > > > > At a high level, does this feature seem useful to users? > > > > > > > > This seems useful, though I am not I would touch the existing > > > options. > > > > I would have gone with a simple -L option (taking the same kind of > > > > input than -l but with new behavior), and not combine a flag with > > > > existing options. > > > > > > > > > > That would be an easier patchset to do up. However, it would then mean > > > that > > > we have no less than 4 different ways to specify the cores to use: "- > > > c", > > > "-l", "-L", "--lcores" - and therefore need 4 different sets of parsing > > > options for them, and more checks to ensure we have only one of the 4 > > > specified in any run. That's why I chose the modifier option, and to > > > try > > > and consolidate the core setup a bit. > > > > > > However, if having a completely new option is preferred, I am happy > > > enough > > > to do up a different patchset for that. > > > > > > > I scanned through the series, not much to say. > > > > Maybe add a unit test for new cmdline option. > > > > > > > Sure. Once it's decided what approach (if any) to take, I'll do up a > > > new > > > patchset, taking into account any relevant feedback on this set. > > > > > > /Bruce > > > > Changing the EAL parameter parser to a "two pass parser" makes sense. > > I think checking for existence of more than one lcore specification options > > should suffice; we don't need to accept multiple lcore specification > > options and check for conflicts. > > There already is a first pass to catch log parameters, could the offset arg > be handled there? > It could, but I'd rather not get into further handling of args in a two-pass setup. If we go that way, we might be better to do a completely "delayed-parsing" setup, where we use getopt to put all arguments into a structure with named pointers for each arg type. Thereafter we do the actual processing of args from the structure itself, allowing us to do all arg processing in a fixed/known order. Unfortunately, that would be a significant change in how things are done.
Also, from the discussion on this thread, there seems to be some support for having a completely new cmdline arg that takes the core list and always remaps them, rather than using a modifier to existing args. Your opinions on the relative benefits/drawbacks of the two approaches are welcome! :-) /Bruce
