Re: [PATCH] ipvs: improved SH fallback strategy
From: Simon Horman <horms@verge.net.au>
Date: 2013-09-25 00:30:43
Also in:
lkml, lvs-devel
On Tue, Sep 24, 2013 at 10:32:38AM +0100, Alexander Frolkin wrote:
Improve the SH fallback realserver selection strategy. With sh and sh-fallback, if a realserver is down, this attempts to distribute the traffic that would have gone to that server evenly among the remaining servers. Signed-off-by: Alexander Frolkin <redacted>
Hi Alexander, could you add some comments to the code or at least a description of the algorithm to the above the function. The intent of original code may not have been obvious to the eye but this version certainly isn't obvious to mine.
quoted hunk ↗ jump to hunk
--diff --git a/net/netfilter/ipvs/ip_vs_sh.c b/net/netfilter/ipvs/ip_vs_sh.c index 3588fae..0db7d01 100644 --- a/net/netfilter/ipvs/ip_vs_sh.c +++ b/net/netfilter/ipvs/ip_vs_sh.c@@ -120,22 +120,33 @@ static inline struct ip_vs_dest * ip_vs_sh_get_fallback(struct ip_vs_service *svc, struct ip_vs_sh_state *s, const union nf_inet_addr *addr, __be16 port) { - unsigned int offset; - unsigned int hash; + unsigned int offset, roffset; + unsigned int hash, ihash; struct ip_vs_dest *dest; - for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) { - hash = ip_vs_sh_hashkey(svc->af, addr, port, offset); - dest = rcu_dereference(s->buckets[hash].dest); - if (!dest) - break; - if (is_unavailable(dest)) - IP_VS_DBG_BUF(6, "SH: selected unavailable server " - "%s:%d (offset %d)", + ihash = ip_vs_sh_hashkey(svc->af, addr, port, 0); + dest = rcu_dereference(s->buckets[ihash].dest); + if (!dest) + return NULL; + if (is_unavailable(dest)) { + IP_VS_DBG_BUF(6, "SH: selected unavailable server " + "%s:%d, reselecting", + IP_VS_DBG_ADDR(svc->af, &dest->addr), + ntohs(dest->port)); + for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) { + roffset = (offset + ihash) % IP_VS_SH_TAB_SIZE; + hash = ip_vs_sh_hashkey(svc->af, addr, port, roffset); + dest = rcu_dereference(s->buckets[hash].dest); + if (is_unavailable(dest)) + IP_VS_DBG_BUF(6, "SH: selected unavailable " + "server %s:%d (offset %d), reselecting", IP_VS_DBG_ADDR(svc->af, &dest->addr), - ntohs(dest->port), offset); - else - return dest; + ntohs(dest->port), roffset); + else + return dest; + } + } else { + return dest; } return NULL; --To unsubscribe from this list: send the line "unsubscribe lvs-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html