RE: [PATCH bpf-next v2 7/8] xdp: remove map_to_flush and map swap detection

John Fastabend
2020-01-08T03:45:26Z

Toke Høiland-Jørgensen wrote:
> John Fastabend <john.fastabend@gmail.com> writes:
>
> > Björn Töpel wrote:
> >> From: Björn Töpel <bjorn.topel@intel.com>
> >>
> >> Now that all XDP maps that can be used with bpf_redirect_map() tracks
> >> entries to be flushed in a global fashion, there is not need to track
> >> that the map has changed and flush from xdp_do_generic_map()
> >> anymore. All entries will be flushed in xdp_do_flush_map().
> >>
> >> This means that the map_to_flush can be removed, and the corresponding
> >> checks. Moving the flush logic to one place, xdp_do_flush_map(), give
> >> a bulking behavior and performance boost.
> >>
> >> Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
> >> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
> >> ---
> >
> > __dev_map_flush() still has rcu_read_lock/unlock() around flush_list by
> > this point, assuming I've followed along correctly. Can we drop those
> > now seeing its per CPU and all list ops are per-cpu inside napi context?
>
> Hmm, I guess so? :)
>
> > Two reasons to consider, with this patch dev_map_flush() is always
> > called even if the list is empty so even in TX case without redirect.
> > But probably more important it makes the locking requirements more clear.
> > Could probably be done in a follow up patch but wanted to bring it up.
>
> This series was already merged, but I'll follow up with the non-map
> redirect change. This requires a bit of refactoring anyway, so I can
> incorporate the lock removal into that...
>
> -Toke
>

Ah I was just catching up with email and missed itwas already applied.

I can also submit a few fixup patches no problem for the comments and this.

.John