Re: [PATCH iproute2-next] tc: use ll_init_map() only when needed

[David Ahern <dsahern@kernel.org>]

Jamal: waiting for your review ...

On 4/28/26 2:28 AM, Eric Dumazet wrote:
> Some setups can have thousands of devices.
> 
> ll_init_map() is rather expensive for them.
> 
> Only call ll_init_map() in the following cases:
> 
> 1) tc runs in batch mode.
> 2) tc runs in monitor mode.
> 3) tc dumps qdiscs/classes/filters for all netdev.
> 
> This greatly reduces RTNL pressure on common operations.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  tc/f_route.c   |  1 -
>  tc/m_mirred.c  |  2 --
>  tc/tc.c        |  1 +
>  tc/tc_class.c  |  6 ++----
>  tc/tc_filter.c | 32 ++++++++++++++++----------------
>  tc/tc_qdisc.c  |  5 ++---
>  6 files changed, 21 insertions(+), 26 deletions(-)
> 
> diff --git a/tc/f_route.c b/tc/f_route.c
> index 96b99b06be179c90dfb0d24d9577b5206dd98ef1..c234ddf0cb9309556844c85047d0f9ef53a2fd7b 100644
> --- a/tc/f_route.c
> +++ b/tc/f_route.c
> @@ -76,7 +76,6 @@ static int route_parse_opt(const struct filter_util *qu, char *handle, int argc,
>  			__u32 id;
>  
>  			NEXT_ARG();
> -			ll_init_map(&rth);
>  			if ((id = ll_name_to_index(*argv)) <= 0) {
>  				fprintf(stderr, "Illegal \"fromif\"\n");
>  				return -1;
> diff --git a/tc/m_mirred.c b/tc/m_mirred.c
> index f4da3c76284460d7f4bb73c7c3c172732f054632..e9ae5199432e828026f15ce226c5f5f84998c660 100644
> --- a/tc/m_mirred.c
> +++ b/tc/m_mirred.c
> @@ -213,8 +213,6 @@ parse_direction(const struct action_util *a, int *argc_p, char ***argv_p,
>  	if (d[0])  {
>  		int idx;
>  
> -		ll_init_map(&rth);
> -
>  		idx = ll_name_to_index(d);
>  		if (!idx)
>  			return nodev(d);
> diff --git a/tc/tc.c b/tc/tc.c
> index 0fc658c881f0f553f1f1f8d87b46943d4d0eed8f..7d69e4d533a98b9c071cb954443a049a52252f2c 100644
> --- a/tc/tc.c
> +++ b/tc/tc.c
> @@ -243,6 +243,7 @@ static int batch(const char *name)
>  		return -1;
>  	}
>  
> +	ll_init_map(&rth);
>  	ret = do_batch(name, force, tc_batch_cmd, NULL);
>  
>  	rtnl_close(&rth);
> diff --git a/tc/tc_class.c b/tc/tc_class.c
> index 6d707d8c924f4b5e90201d4de8e9779f82ce17f3..9aace019e6c8b96fb51edb4fe89bea5b7469beed 100644
> --- a/tc/tc_class.c
> +++ b/tc/tc_class.c
> @@ -136,11 +136,11 @@ static int tc_class_modify(int cmd, unsigned int flags, int argc, char **argv)
>  	}
>  
>  	if (d[0])  {
> -		ll_init_map(&rth);
> -
>  		req.t.tcm_ifindex = ll_name_to_index(d);
>  		if (!req.t.tcm_ifindex)
>  			return -nodev(d);
> +	} else {
> +		ll_init_map(&rth);
>  	}
>  
>  	if (rtnl_talk(&rth, &req.n, NULL) < 0)
> @@ -437,8 +437,6 @@ static int tc_class_list(int argc, char **argv)
>  		argc--; argv++;
>  	}
>  
> -	ll_init_map(&rth);
> -
>  	if (d[0]) {
>  		t.tcm_ifindex = ll_name_to_index(d);
>  		if (!t.tcm_ifindex)
> diff --git a/tc/tc_filter.c b/tc/tc_filter.c
> index 7db850bda11a3408ec66b457c9fc590f3a734f65..be70e360849e5058192640da0f061810a99e2ea8 100644
> --- a/tc/tc_filter.c
> +++ b/tc/tc_filter.c
> @@ -188,16 +188,17 @@ static int tc_filter_modify(int cmd, unsigned int flags, int argc, char **argv)
>  		addattr_l(&req.n, sizeof(req), TCA_KIND, k, strlen(k)+1);
>  
>  	if (d[0])  {
> -		ll_init_map(&rth);
> -
>  		req.t.tcm_ifindex = ll_name_to_index(d);
>  		if (req.t.tcm_ifindex == 0) {
>  			fprintf(stderr, "Cannot find device \"%s\"\n", d);
>  			return 1;
>  		}
> -	} else if (block_index) {
> -		req.t.tcm_ifindex = TCM_IFINDEX_MAGIC_BLOCK;
> -		req.t.tcm_block_index = block_index;
> +	} else {
> +		ll_init_map(&rth);
> +		if (block_index) {
> +			req.t.tcm_ifindex = TCM_IFINDEX_MAGIC_BLOCK;
> +			req.t.tcm_block_index = block_index;
> +		}
>  	}
>  
>  	if (q) {
> @@ -539,8 +540,6 @@ static int tc_filter_get(int cmd, unsigned int flags, int argc, char **argv)
>  	}
>  
>  	if (d[0])  {
> -		ll_init_map(&rth);
> -
>  		req.t.tcm_ifindex = ll_name_to_index(d);
>  		if (!req.t.tcm_ifindex)
>  			return -nodev(d);
> @@ -704,21 +703,22 @@ static int tc_filter_list(int cmd, int argc, char **argv)
>  
>  	req.t.tcm_info = TC_H_MAKE(prio<<16, protocol);
>  
> -	ll_init_map(&rth);
> -
>  	if (d[0]) {
>  		req.t.tcm_ifindex = ll_name_to_index(d);
>  		if (!req.t.tcm_ifindex)
>  			return -nodev(d);
>  		filter_ifindex = req.t.tcm_ifindex;
> -	} else if (block_index) {
> -		if (!tc_qdisc_block_exists(block_index)) {
> -			fprintf(stderr, "Cannot find block \"%u\"\n", block_index);
> -			return 1;
> +	} else {
> +		ll_init_map(&rth);
> +		if (block_index) {
> +			if (!tc_qdisc_block_exists(block_index)) {
> +				fprintf(stderr, "Cannot find block \"%u\"\n", block_index);
> +				return 1;
> +			}
> +			req.t.tcm_ifindex = TCM_IFINDEX_MAGIC_BLOCK;
> +			req.t.tcm_block_index = block_index;
> +			filter_block_index = block_index;
>  		}
> -		req.t.tcm_ifindex = TCM_IFINDEX_MAGIC_BLOCK;
> -		req.t.tcm_block_index = block_index;
> -		filter_block_index = block_index;
>  	}
>  
>  	if (filter_chain_index_set)
> diff --git a/tc/tc_qdisc.c b/tc/tc_qdisc.c
> index 7eb9a31baa31fb91a8141c9eca1135e76a52fa8b..252ea861f249a5a71cf782389776e68c3e48c6cc 100644
> --- a/tc/tc_qdisc.c
> +++ b/tc/tc_qdisc.c
> @@ -193,8 +193,6 @@ static int tc_qdisc_modify(int cmd, unsigned int flags, int argc, char **argv)
>  	if (d[0])  {
>  		int idx;
>  
> -		ll_init_map(&rth);
> -
>  		idx = ll_name_to_index(d);
>  		if (!idx)
>  			return -nodev(d);
> @@ -411,13 +409,14 @@ static int tc_qdisc_list(int argc, char **argv)
>  		argc--; argv++;
>  	}
>  
> -	ll_init_map(&rth);
>  
>  	if (d[0]) {
>  		req.t.tcm_ifindex = ll_name_to_index(d);
>  		if (!req.t.tcm_ifindex)
>  			return -nodev(d);
>  		filter_ifindex = req.t.tcm_ifindex;
> +	} else {
> +		ll_init_map(&rth);
>  	}
>  
>  	if (dump_invisible) {