Re: [PATCH] dumpcap: fix mbuf pool ring type

[Stephen Hemminger <stephen@networkplumber.org>]

On Mon, 2 Oct 2023 10:42:53 +0200
Morten Brørup <mb@smartsharesystems.com> wrote:

> > Switching to rte_pktmbuf_pool_create() still leaves the user with the
> > possibility to shoot himself in the foot (I was thinking of setting
> > some --mbuf-pool-ops-name EAL option).
> > 
> > This application has explicit requirements in terms of concurrent
> > access (and I don't think the mempool library exposes per driver
> > capabilities in that regard).
> > The application was enforcing the use of mempool/ring so far.
> > 
> > I think it is safer to go with an explicit
> > rte_pktmbuf_pool_create_by_ops(... "ring_mp_mc").
> > WDYT?  
> 
> <feature creep>
> Or perhaps one of "ring_mt_rts" or "ring_mt_hts", if any of those mbuf pool drivers are specified on the command line; otherwise fall back to "ring_mp_mc".
> 
> Actually, I prefer Stephen's suggestion of using the default mbuf pool driver. The option is there for a reason.
> 
> However, David is right: We want to prevent the user from using a thread-unsafe mempool driver in this use case.
> 
> And I guess there might be other use cases than this one, where a thread-safe mempool driver is required. So adding a generalized function to get the "upgraded" (i.e. thread safe) variant of a mempool driver would be nice.
> </feature creep>

If the user overrides the default mbuf pool type, then it will need to be thread safe for
the general case of driver as well (or they are on single cpu). 


I think the patch should be applied as is.