nfp: bpf: add simple map op cache

Each get_next and lookup call requires a round trip to the device.
However, the device is capable of giving us a few entries back,
instead of just one.

In this patch we ask for a small yet reasonable number of entries
(4) on every get_next call, and on subsequent get_next/lookup calls
check this little cache for a hit. The cache is only kept for 250us,
and is invalidated on every operation which may modify the map
(e.g. delete or update call). Note that operations may be performed
simultaneously, so we have to keep track of operations in flight.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 23 insertions, 0 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/main.h b/drivers/net/ethernet/netronome/nfp/bpf/main.h
index f4802036eb42..fac9c6f9e197 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/main.h
+++ b/drivers/net/ethernet/netronome/nfp/bpf/main.h
@@ -99,6 +99,7 @@ enum pkt_vec {
  * @maps_neutral:	hash table of offload-neutral maps (on pointer)
  *
  * @abi_version:	global BPF ABI version
+ * @cmsg_cache_cnt:	number of entries to read for caching
  *
  * @adjust_head:	adjust head capability
  * @adjust_head.flags:		extra flags for adjust head
@@ -124,6 +125,7 @@ enum pkt_vec {
  * @pseudo_random:	FW initialized the pseudo-random machinery (CSRs)
  * @queue_select:	BPF can set the RX queue ID in packet vector
  * @adjust_tail:	BPF can simply trunc packet size for adjust tail
+ * @cmsg_multi_ent:	FW can pack multiple map entries in a single cmsg
  */
 struct nfp_app_bpf {
 	struct nfp_app *app;
@@ -134,6 +136,8 @@ struct nfp_app_bpf {
 	unsigned int cmsg_key_sz;
 	unsigned int cmsg_val_sz;
 
+	unsigned int cmsg_cache_cnt;
+
 	struct list_head map_list;
 	unsigned int maps_in_use;
 	unsigned int map_elems_in_use;
@@ -169,6 +173,7 @@ struct nfp_app_bpf {
 	bool pseudo_random;
 	bool queue_select;
 	bool adjust_tail;
+	bool cmsg_multi_ent;
 };
 
 enum nfp_bpf_map_use {
@@ -183,11 +188,21 @@ struct nfp_bpf_map_word {
 	unsigned char non_zero_update	:1;
 };
 
+#define NFP_BPF_MAP_CACHE_CNT		4U
+#define NFP_BPF_MAP_CACHE_TIME_NS	(250 * 1000)
+
 /**
  * struct nfp_bpf_map - private per-map data attached to BPF maps for offload
  * @offmap:	pointer to the offloaded BPF map
  * @bpf:	back pointer to bpf app private structure
  * @tid:	table id identifying map on datapath
+ *
+ * @cache_lock:	protects @cache_blockers, @cache_to, @cache
+ * @cache_blockers:	number of ops in flight which block caching
+ * @cache_gen:	counter incremented by every blocker on exit
+ * @cache_to:	time when cache will no longer be valid (ns)
+ * @cache:	skb with cached response
+ *
  * @l:		link on the nfp_app_bpf->map_list list
  * @use_map:	map of how the value is used (in 4B chunks)
  */
@@ -195,6 +210,13 @@ struct nfp_bpf_map {
 	struct bpf_offloaded_map *offmap;
 	struct nfp_app_bpf *bpf;
 	u32 tid;
+
+	spinlock_t cache_lock;
+	u32 cache_blockers;
+	u32 cache_gen;
+	u64 cache_to;
+	struct sk_buff *cache;
+
 	struct list_head l;
 	struct nfp_bpf_map_word use_map[];
 };
@@ -566,6 +588,7 @@ void *nfp_bpf_relo_for_vnic(struct nfp_prog *nfp_prog, struct nfp_bpf_vnic *bv);
 
 unsigned int nfp_bpf_ctrl_cmsg_min_mtu(struct nfp_app_bpf *bpf);
 unsigned int nfp_bpf_ctrl_cmsg_mtu(struct nfp_app_bpf *bpf);
+unsigned int nfp_bpf_ctrl_cmsg_cache_cnt(struct nfp_app_bpf *bpf);
 long long int
 nfp_bpf_ctrl_alloc_map(struct nfp_app_bpf *bpf, struct bpf_map *map);
 void