Re: [dpdk-dev] [PATCH v1 02/15] eal: new eal option '--lcores' for cpu assignment

[Bruce Richardson <bruce.richardson@intel.com>]

On Thu, Jan 22, 2015 at 02:34:07PM +0000, Ananyev, Konstantin wrote:
> Hi Bruce,
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Bruce Richardson
> > Sent: Thursday, January 22, 2015 12:19 PM
> > To: Liang, Cunming
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH v1 02/15] eal: new eal option '--lcores' for cpu assignment
> > 
> > On Thu, Jan 22, 2015 at 04:16:25PM +0800, Cunming Liang wrote:
> > > It supports one new eal long option '--lcores' for EAL thread cpuset assignment.
> > >
> > > The format pattern:
> > > 	--lcores='lcores[@cpus]<,lcores[@cpus]>'
> > > lcores, cpus could be a single digit or a group.
> > > '(' and ')' are necessary if it's a group.
> > > If not supply '@cpus', the value of cpus uses the same as lcores.
> > >
> > > e.g. '1,2@(5-7),(3-5)@(0,2),(0,6)' means starting 7 EAL thread as below
> > >   lcore 0 runs on cpuset 0x41 (cpu 0,6)
> > >   lcore 1 runs on cpuset 0x2 (cpu 1)
> > >   lcore 2 runs on cpuset 0xe0 (cpu 5,6,7)
> > >   lcore 3,4,5 runs on cpuset 0x5 (cpu 0,2)
> > >   lcore 6 runs on cpuset 0x41 (cpu 0,6)
> > >
> > 
> > This strikes me as very confusing, though a couple of tweaks might help with
> > readability. The lcore 0 at the end is especially confusing.
> 
> Didn't get you here: do you find (0,6) confusing, right?
> Because braces implicitly specifies affinity for group of en-braced lcores? 
> 
> > Perhaps we can
> > limit the allowed formats here,
> > * require the lcore_id to be specified - the lack of an lcore id for the last part
> > makes having it as lcore 0 surprising.
> 
> Again, not sure I understand you properly:  lcore_id(s) are always specified explicitly. 
> Physical cpus part might be omitted.
> 
> > * only allow one lcore id to be given for each set of cores.
> 
> So you mean for '(3-5)@(0,2)' user would have to: '3@(0,2),4@(0,2),5@(0,2)'?
> I don't see big difference here, but imagine you'd like to create a pool of 32 EAL-threads running on same cpu set.
> With current syntax it is just something like: '(32-63)@(0-7)'.
> With what you proposing it will be a very long list.  
> 
> > 
> > I think it may still be readable if we allow the core set to be omitted if its
> > to be the same as the lcore_id.
> 
> I think that is supported.
> See lcore_id=1 in Steve's example above.
> As I understand: --lcores='0,2,3-5' is equal to '-l 0,2,3-5' and to '-c 0x3d'.
> 
> Konstantin

Ok, thanks for the clarification.

/Bruce