When queueing a set element add or removal operation to the transaction
log, check if the previous operation already asks for a the identical
operation on the same set.
If so, store the element reference in the preceding operation.
This significantlty reduces memory consumption when many set add/delete
operations appear in a single transaction.
Example: 10k elements require 937kb of memory (10k allocations from
kmalloc-96 slab).
Assuming we can compact 4 elements in the same set, 468 kbytes
are needed (64 bytes for base struct, nft_trans_elemn, 32 bytes
for nft_trans_one_elem structure, so 2500 allocations from kmalloc-192
slab).
For large batch updates we can compact up to 62 elements
into one single nft_trans_elem structure (~65% mem reduction):
(64 bytes for base struct, nft_trans_elem, 32 byte for nft_trans_one_elem
struct).
We can halve size of nft_trans_one_elem struct by moving
timeout/expire/update_flags into a dynamically allocated structure,
this allows to store 124 elements in a 2k slab nft_trans_elem struct.
This is done in a followup patch.
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
---
net/netfilter/nf_tables_api.c | 90 +++++++++++++++++++++++++++++++++++
1 file changed, 90 insertions(+)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 5b5178841553..679312d71bbe 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -26,6 +26,9 @@
#define NFT_MODULE_AUTOLOAD_LIMIT (MODULE_NAME_LEN - sizeof("nft-expr-255-"))
#define NFT_SET_MAX_ANONLEN 16
+/* limit compaction to avoid huge kmalloc/krealloc sizes. */
+#define NFT_MAX_SET_NELEMS ((2048 - sizeof(struct nft_trans_elem)) / sizeof(struct nft_trans_one_elem))
+
unsigned int nf_tables_net_id __read_mostly;
static LIST_HEAD(nf_tables_expressions);
@@ -391,6 +394,86 @@ static void nf_tables_unregister_hook(struct net *net,
return __nf_tables_unregister_hook(net, table, chain, false);
}
+static bool nft_trans_collapse_set_elem_allowed(const struct nft_trans_elem *a, const struct nft_trans_elem *b)
+{
+ /* NB: the ->bound equality check is defensive, at this time we only merge
+ * a new nft_trans_elem transaction request with the transaction tail
+ * element, but a->bound != b->bound would imply a NEWRULE transaction
+ * is queued in-between.
+ *
+ * The set check is mandatory, the NFT_MAX_SET_NELEMS check prevents
+ * huge krealloc() requests.
+ */
+ return a->set == b->set && a->bound == b->bound && a->nelems < NFT_MAX_SET_NELEMS;
+}
+
+static bool nft_trans_collapse_set_elem(struct nftables_pernet *nft_net,
+ struct nft_trans_elem *tail,
+ struct nft_trans_elem *trans,
+ gfp_t gfp)
+{
+ unsigned int nelems, old_nelems = tail->nelems;
+ struct nft_trans_elem *new_trans;
+
+ if (!nft_trans_collapse_set_elem_allowed(tail, trans))
+ return false;
+
+ /* "cannot happen", at this time userspace element add
+ * requests always allocate a new transaction element.
+ *
+ * This serves as a reminder to adjust the list_add_tail
+ * logic below in case this ever changes.
+ */
+ if (WARN_ON_ONCE(trans->nelems != 1))
+ return false;
+
+ if (check_add_overflow(old_nelems, trans->nelems, &nelems))
+ return false;
+
+ /* krealloc might free tail which invalidates list pointers */
+ list_del_init(&tail->nft_trans.list);
+
+ new_trans = krealloc(tail, struct_size(tail, elems, nelems), gfp);
+ if (!new_trans) {
+ list_add_tail(&tail->nft_trans.list, &nft_net->commit_list);
+ return false;
+ }
+
+ /*
+ * new_trans->nft_trans.list contains garbage, but
+ * list_add_tail() doesn't care.
+ */
+ new_trans->nelems = nelems;
+ new_trans->elems[old_nelems] = trans->elems[0];
+ list_add_tail(&new_trans->nft_trans.list, &nft_net->commit_list);
+
+ return true;
+}
+
+static bool nft_trans_try_collapse(struct nftables_pernet *nft_net,
+ struct nft_trans *trans, gfp_t gfp)
+{
+ struct nft_trans *tail;
+
+ if (list_empty(&nft_net->commit_list))
+ return false;
+
+ tail = list_last_entry(&nft_net->commit_list, struct nft_trans, list);
+
+ if (tail->msg_type != trans->msg_type)
+ return false;
+
+ switch (trans->msg_type) {
+ case NFT_MSG_NEWSETELEM:
+ case NFT_MSG_DELSETELEM:
+ return nft_trans_collapse_set_elem(nft_net,
+ nft_trans_container_elem(tail),
+ nft_trans_container_elem(trans), gfp);
+ }
+
+ return false;
+}
+
static void nft_trans_commit_list_add_tail(struct net *net, struct nft_trans *trans)
{
struct nftables_pernet *nft_net = nft_pernet(net);
@@ -424,11 +507,18 @@ static void nft_trans_commit_list_add_tail(struct net *net, struct nft_trans *tr
static void nft_trans_commit_list_add_elem(struct net *net, struct nft_trans *trans,
gfp_t gfp)
{
+ struct nftables_pernet *nft_net = nft_pernet(net);
+
WARN_ON_ONCE(trans->msg_type != NFT_MSG_NEWSETELEM &&
trans->msg_type != NFT_MSG_DELSETELEM);
might_alloc(gfp);
+ if (nft_trans_try_collapse(nft_net, trans, gfp)) {
+ kfree(trans);
+ return;
+ }
+
nft_trans_commit_list_add_tail(net, trans);
}
--
2.45.2
