MEDIUM: stick-tables: Limit the number of old entries we remove

Limit the number of old entries we remove in one call of
stktable_trash_oldest(), as we do so while holding the heavily contended
update write lock, so we'd rather not hold it for too long.
This helps getting stick tables perform better under heavy load.

(cherry picked from commit d2d4c3eb6566145d30eb38dc96b2b79d3f1db8fc)
[wt: backported since situation encountered in 3.1 as well without this
 patch. It also contains the definition for STKTABLE_MAX_UPDATES_AT_ONCE
 from the previous commit]
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/include/haproxy/defaults.h b/include/haproxy/defaults.h
index 88ab35b..660edc9 100644 (file)
--- a/include/haproxy/defaults.h
+++ b/include/haproxy/defaults.h
@@ -589,4 +589,8 @@
 # define DEBUG_MEMORY_POOLS 1
 #endif
 
+#ifndef STKTABLE_MAX_UPDATES_AT_ONCE
+#define STKTABLE_MAX_UPDATES_AT_ONCE 100
+#endif /* STKTABLE_MAX_UPDATES_AT_ONCE */
+
 #endif /* _HAPROXY_DEFAULTS_H */

diff --git a/src/stick_table.c b/src/stick_table.c
index 26ec6a4..0f1cb82 100644 (file)
--- a/src/stick_table.c
+++ b/src/stick_table.c
@@ -267,8 +267,8 @@ int stktable_trash_oldest(struct stktable *t, int to_batch)
 {
        struct stksess *ts;
        struct eb32_node *eb;
-       int max_search = to_batch * 2; // no more than 50% misses
-       int max_per_shard = (to_batch + CONFIG_HAP_TBL_BUCKETS - 1) / CONFIG_HAP_TBL_BUCKETS;
+       int max_search; // no more than 50% misses
+       int max_per_shard;
        int done_per_shard;
        int batched = 0;
        int updt_locked;
@@ -277,6 +277,12 @@ int stktable_trash_oldest(struct stktable *t, int to_batch)
 
        shard = 0;
 
+       if (to_batch > STKTABLE_MAX_UPDATES_AT_ONCE)
+               to_batch = STKTABLE_MAX_UPDATES_AT_ONCE;
+
+       max_search = to_batch * 2; // no more than 50% misses
+       max_per_shard = (to_batch + CONFIG_HAP_TBL_BUCKETS - 1) / CONFIG_HAP_TBL_BUCKETS;
+
        while (batched < to_batch) {
                done_per_shard = 0;
                looped = 0;