Re: [PATCH net-next 2/3] ipv4: rate limit updating of next hop exceptions with same pmtu
From: Julian Anastasov <ja@ssi.bg>
Date: 2013-05-28 08:42:12
Hello, On Tue, 28 May 2013, Timo Teräs wrote:
quoted hunk ↗ jump to hunk
The tunnel devices call update_pmtu for each packet sent, this causes contention on the fnhe_lock. Ignore the pmtu update if pmtu is not actually changed, and there is still plenty of time before the entry expires. Signed-off-by: Timo Teräs <redacted> --- net/ipv4/route.c | 4 ++++ 1 file changed, 4 insertions(+)diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 561a378..a4082be 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c@@ -947,6 +947,10 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu) if (mtu < ip_rt_min_pmtu) mtu = ip_rt_min_pmtu; + if (rt->rt_pmtu == mtu && + time_before(jiffies, dst->expires - ip_rt_mtu_expires / 2)) + return; +
Can we also add logic in this patch in
update_or_create_fnhe, so that we avoid invalidation for cached
routes when only pmtu expiration is updated (same pmtu), i.e.:
+ if (gw || pmtu != fnhe->fnhe_pmtu) {
+ /* Exception created; mark the cached routes for the nexthop
+ ...
+ }
BTW, I now see that previous patch should
call for_each_possible_cpu for the both cases, not
only when fnhe is created but also on update:
bool invalidate;
if (fnhe) {
invalidate = gw || pmtu != fnhe->fnhe_pmtu;
...
} else {
...
invalidate = true;
}
if (invalidate) {
/* Exception created; mark the cached routes for the nexthop
...
}
Regards
--
Julian Anastasov [off-list ref]