Commit 33990010 authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman

rhashtable: reorganize struct rhashtable layout

commit e5d672a0780d9e7118caad4c171ec88b8299398d upstream.

While under frags DDOS I noticed unfortunate false sharing between
@nelems and @params.automatic_shrinking

Move @nelems at the end of struct rhashtable so that first cache line
is shared between all cpus, because almost never dirtied.
Signed-off-by: default avatarEric Dumazet <>
Signed-off-by: default avatarDavid S. Miller <>
Signed-off-by: default avatarBen Hutchings <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent bf818734
......@@ -133,23 +133,23 @@ struct rhashtable_params {
* struct rhashtable - Hash table handle
* @tbl: Bucket table
* @nelems: Number of elements in table
* @key_len: Key length for hashfn
* @elasticity: Maximum chain length before rehash
* @p: Configuration parameters
* @run_work: Deferred worker to expand/shrink asynchronously
* @mutex: Mutex to protect current/future table swapping
* @lock: Spin lock to protect walker list
* @nelems: Number of elements in table
struct rhashtable {
struct bucket_table __rcu *tbl;
atomic_t nelems;
unsigned int key_len;
unsigned int elasticity;
struct rhashtable_params p;
struct work_struct run_work;
struct mutex mutex;
spinlock_t lock;
atomic_t nelems;
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