From: Theo Buehler <tb@theobuehler.org>
Subject: Re: bgpd: resize communities with reallocarray
To: tech@openbsd.org
Date: Thu, 13 Nov 2025 16:02:33 +0100

On Thu, Nov 13, 2025 at 04:00:06PM +0100, Claudio Jeker wrote:
> insert_community() is part of the hot path especially when people use
> communities to tag internally for their filters.
> Using recallocarray() there is a bit problematic since it has a much
> higher overhead than any realloc verision.
> Use reallocarray() and memset() instead.
> 
> In one of my IXP test setups insert_community is called 224 million times
> during initial sync.

ouch.

ok tb

> -- 
> :wq Claudio
> 
> Index: rde_community.c
> ===================================================================
> RCS file: /cvs/src/usr.sbin/bgpd/rde_community.c,v
> diff -u -p -r1.18 rde_community.c
> --- rde_community.c	4 Nov 2025 14:43:22 -0000	1.18
> +++ rde_community.c	13 Nov 2025 14:28:42 -0000
> @@ -227,9 +227,10 @@ insert_community(struct rde_community *c
>  		struct community *new;
>  		int newsize = comm->size + 8;
>  
> -		if ((new = recallocarray(comm->communities, comm->size,
> -		    newsize, sizeof(struct community))) == NULL)
> +		if ((new = reallocarray(comm->communities, newsize,
> +		    sizeof(struct community))) == NULL)
>  			fatal(__func__);
> +		memset(&new[comm->size], 0, sizeof(struct community) * 8);
>  		comm->communities = new;
>  		comm->size = newsize;
>  	}
>