[PATCH v3 16/30] rhashtable: reorganize struct rhashtable layout

Stephen Hemminger
2018-09-13T14:58:48Z

From: Eric Dumazet <edumazet@google.com>

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: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit e5d672a0780d9e7118caad4c171ec88b8299398d)
---
include/linux/rhashtable.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 7fd514f36e74..a4be6388a980 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -152,25 +152,25 @@ struct rhashtable_params {
/**
* struct rhashtable - Hash table handle
* @tbl: Bucket table
- * @nelems: Number of elements in table
* @key_len: Key length for hashfn
- * @p: Configuration parameters
* @max_elems: Maximum number of elements in table
+ * @p: Configuration parameters
* @rhlist: True if this is an rhltable
* @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;
- struct rhashtable_params p;
unsigned int max_elems;
+ struct rhashtable_params p;
bool rhlist;
struct work_struct run_work;
struct mutex mutex;
spinlock_t lock;
+ atomic_t nelems;
};

/**
--
2.18.0