From: YOSHIFUJI Hideaki <hideaki.yoshifuji@miraclelinux.com>
To: Martin KaFai Lau <kafai@fb.com>, netdev <netdev@vger.kernel.org>
Cc: hideaki.yoshifuji@miraclelinux.com,
Kernel Team <kernel-team@fb.com>,
Hannes Frederic Sowa <hannes@stressinduktion.org>,
Julian Anastasov <ja@ssi.bg>
Subject: Re: [PATCH net-next v2 2/2] ipv6: Avoid rt6_probe() taking writer lock in the fast path
Date: Tue, 28 Jul 2015 09:17:41 +0900 [thread overview]
Message-ID: <55B6CA25.4040909@miraclelinux.com> (raw)
In-Reply-To: <1437757063-1186401-3-git-send-email-kafai@fb.com>
Hi,
Martin KaFai Lau wrote:
> The patch checks neigh->nud_state before acquiring the writer lock.
> Note that rt6_probe() is only used in CONFIG_IPV6_ROUTER_PREF.
>
> 40 udpflood processes and a /64 gateway route are used.
> The gateway has NUD_PERMANENT. Each of them is run for 30s.
> At the end, the total number of finished sendto():
>
> Before: 55M
> After: 95M
I think it is better to describe why it is okay without any locks.
--yoshfuji
>
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
> CC: Julian Anastasov <ja@ssi.bg>
> CC: YOSHIFUJI Hideaki <hideaki.yoshifuji@miraclelinux.com>
> ---
> net/ipv6/route.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 6d503db..76dcff8 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -560,6 +560,9 @@ static void rt6_probe(struct rt6_info *rt)
> rcu_read_lock_bh();
> neigh = __ipv6_neigh_lookup_noref(rt->dst.dev, &rt->rt6i_gateway);
> if (neigh) {
> + if (neigh->nud_state & NUD_VALID)
> + goto out;
> +
> work = NULL;
> write_lock(&neigh->lock);
> if (!(neigh->nud_state & NUD_VALID) &&
> @@ -583,6 +586,7 @@ static void rt6_probe(struct rt6_info *rt)
> schedule_work(&work->work);
> }
>
> +out:
> rcu_read_unlock_bh();
> }
> #else
>
--
Hideaki Yoshifuji <hideaki.yoshifuji@miraclelinux.com>
Technical Division, MIRACLE LINUX CORPORATION
next prev parent reply other threads:[~2015-07-28 0:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-24 16:57 [PATCH net-next v2 0/2] ipv6: Avoid rt6_probe() taking writer lock in the fast path Martin KaFai Lau
2015-07-24 16:57 ` [PATCH net-next v2 1/2] ipv6: Re-arrange code in rt6_probe() Martin KaFai Lau
2015-07-28 0:07 ` YOSHIFUJI Hideaki/吉藤英明
2015-07-24 16:57 ` [PATCH net-next v2 2/2] ipv6: Avoid rt6_probe() taking writer lock in the fast path Martin KaFai Lau
2015-07-28 0:17 ` YOSHIFUJI Hideaki [this message]
2015-07-27 8:08 ` [PATCH net-next v2 0/2] " David Miller
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