MAJOR: pattern: add LRU-based cache on pattern matching
The principle of this cache is to have a global cache for all pattern
matching operations which rely on lists (reg, sub, dir, dom, ...). The
input data, the expression and a random seed are used as a hashing key.
The cached entries contains a pointer to the expression and a revision
number for that expression so that we don't accidently used obsolete
data after a pattern update or a very unlikely hash collision.
Regarding the risk of collisions, 10k entries at 10k req/s mean 1% risk
of a collision after 60 years, that's already much less than the memory's
reliability in most machines and more durable than most admin's life
expectancy. A collision will result in a valid result to be returned
for a different entry from the same list. If this is not acceptable,
the cache can be disabled using tune.pattern.cache-size.
A test on a file containing 10k small regex showed that the regex
matching was limited to 6k/s instead of 70k with regular strings.
When enabling the LRU cache, the performance was back to 70k/s.
diff --git a/src/haproxy.c b/src/haproxy.c
index 474179c..5822a8b 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -146,6 +146,7 @@
.maxrewrite = MAXREWRITE,
.chksize = BUFSIZE,
.reserved_bufs = RESERVED_BUFS,
+ .pattern_cache = DEFAULT_PAT_LRU_SIZE,
#ifdef USE_OPENSSL
.sslcachesize = SSLCACHESIZE,
.ssl_default_dh_param = SSL_DEFAULT_DH_PARAM,