Re: [PATCH nf,v4] netfilter: nft_set_rbtree: revisit array resize logic

Pablo Neira Ayuso
2026-03-18T17:04:20Z

On Wed, Mar 18, 2026 at 10:46:56AM -0500, Chris Arges wrote:
> On 2026-03-17 18:07:21, Pablo Neira Ayuso wrote:
> > Chris Arges reports high memory consumption with thousands of
> > containers, this patch revisits the array allocation logic.
> >
> > For anonymous sets, start by 16 slots (which takes 256 bytes on x86_64).
> > Expand it by x2 until threshold of 512 slots is reached, over that
> > threshold, expand it by x1.5.
> >
> > For non-anonymous set, start by 1024 slots in the array (which takes 16
> > Kbytes initially on x86_64). Expand it by x1.5.
> >
> > Use set->ndeact to subtract deactivated elements when calculating the
> > number of the slots in the array, otherwise the array size array gets
> > increased artifically. Add special case shrink logic to deal with flush
> > set too.
> >
> > The shrink logic is skipped by anonymous sets.
> >
> > Use check_add_overflow() to calculate the new array size.
> >
> > Add a WARN_ON_ONCE check to make sure elements fit into the new array
> > size.
> >
> > Reported-by: Chris Arges <carges@cloudflare.com>
> > Fixes: 7e43e0a1141d ("netfilter: nft_set_rbtree: translate rbtree to array for binary search")
> > Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> > ---
> > v4: use maybe_grow: goto tag instead of grow:
> > Add note in commit description: "The shrink logic is skipped by anonymous sets."
> >
>
> I will be able to testing this more in depth early next week. Just to confirm,
> this patch requires this to be applied first?
> https://lore.kernel.org/netfilter-devel/20260307001124.2897063-1-pablo@netfilter.org/

Yes, it requires that fix to be applied first.