On Mon, Aug 07, 2023 at 11:11:04PM +0200, Thomas Gleixner wrote:
On Mon, Aug 07 2023 at 14:18, Peter Zijlstra wrote:
quoted
/**
* futex_hash - Return the hash bucket in the global hash
* @key: Pointer to the futex key for which the hash is calculated
@@ -114,10 +137,29 @@ late_initcall(fail_futex_debugfs);
*/
struct futex_hash_bucket *futex_hash(union futex_key *key)
{
- u32 hash = jhash2((u32 *)key, offsetof(typeof(*key), both.offset) / 4,
+ u32 hash = jhash2((u32 *)key,
+ offsetof(typeof(*key), both.offset) / sizeof(u32),
key->both.offset);
+ int node = key->both.node;
+
+ if (node == -1) {
NUMA_NO_NODE please all over the place.
Ah, so our (futex2) ABI states this needs to be -1, but in theory
someone could come along and change the kernel internal NUMA_NO_NODE to
something else.
That is, I explicitly chose not to use it. I can of course, because as
of now these values do match.
quoted
+ /*
+ * In case of !FLAGS_NUMA, use some unused hash bits to pick a
+ * node -- this ensures regular futexes are interleaved across
+ * the nodes and avoids having to allocate multiple
+ * hash-tables.
+ *
+ * NOTE: this isn't perfectly uniform, but it is fast and
+ * handles sparse node masks.
+ */
+ node = (hash >> futex_hashshift) % nr_node_ids;
+ if (!node_possible(node)) {
+ node = find_next_bit_wrap(node_possible_map.bits,
+ nr_node_ids, node);
+ }
Smart.
Thanks :-)
quoted
+static inline unsigned int futex_size(unsigned int flags)
+{
+ return 1 << (flags & FLAGS_SIZE_MASK);
+}
+
static inline bool futex_flags_valid(unsigned int flags)
If you reorder these two functions in the patch which introduces them,
this diff gets readable :)
Durr, I knew I was forgetting something, will do.