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authorJakub Kicinski <kuba@kernel.org>2024-04-15 11:19:58 -0700
committerJakub Kicinski <kuba@kernel.org>2024-04-15 11:19:58 -0700
commit77c842caa772044db9f8517a03d33df779f9517c (patch)
treec35d85cdf08a651df1049f026d4e6c4eb2dcd178 /lib
parent444cde13826bb4d3f9fdf829bf5e2f7bb03d9c32 (diff)
parent4ba67ef3a1fbb7d8dc5f00de9b93a583d05b38cc (diff)
Merge branch 'net-dqs-optimize-if-stall-threshold-is-not-set'
Breno Leitao says: ==================== net: dqs: optimize if stall threshold is not set Here are four patches aimed at enhancing the Dynamic Queue Limit (DQL) subsystem within the networking stack. The first two commits involve code refactoring, while the third patch introduces the actual change. The fourth patch just improves the cache locality. Typically, when DQL is enabled, stall information is always populated through dql_queue_stall(). However, this information is only necessary if a stall threshold is set, which is stored in struct dql->stall_thrs. Although dql_queue_stall() is relatively inexpensive, it is not entirely free due to memory barriers and similar overheads. To optimize performance, refrain from calling dql_queue_stall() when no stall threshold is set, thus avoiding the processing of unnecessary information. v1: https://lore.kernel.org/all/20240404145939.3601097-1-leitao@debian.org/ ==================== Link: https://lore.kernel.org/r/20240411192241.2498631-1-leitao@debian.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/dynamic_queue_limits.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c
index a1389db1c30a..e49deddd3de9 100644
--- a/lib/dynamic_queue_limits.c
+++ b/lib/dynamic_queue_limits.c
@@ -15,12 +15,10 @@
#define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0)
#define AFTER_EQ(A, B) ((int)((A) - (B)) >= 0)
-static void dql_check_stall(struct dql *dql)
+static void dql_check_stall(struct dql *dql, unsigned short stall_thrs)
{
- unsigned short stall_thrs;
unsigned long now;
- stall_thrs = READ_ONCE(dql->stall_thrs);
if (!stall_thrs)
return;
@@ -86,9 +84,16 @@ void dql_completed(struct dql *dql, unsigned int count)
{
unsigned int inprogress, prev_inprogress, limit;
unsigned int ovlimit, completed, num_queued;
+ unsigned short stall_thrs;
bool all_prev_completed;
num_queued = READ_ONCE(dql->num_queued);
+ /* Read stall_thrs in advance since it belongs to the same (first)
+ * cache line as ->num_queued. This way, dql_check_stall() does not
+ * need to touch the first cache line again later, reducing the window
+ * of possible false sharing.
+ */
+ stall_thrs = READ_ONCE(dql->stall_thrs);
/* Can't complete more than what's in queue */
BUG_ON(count > num_queued - dql->num_completed);
@@ -178,7 +183,7 @@ void dql_completed(struct dql *dql, unsigned int count)
dql->num_completed = completed;
dql->prev_num_queued = num_queued;
- dql_check_stall(dql);
+ dql_check_stall(dql, stall_thrs);
}
EXPORT_SYMBOL(dql_completed);