netdev - Re: [PATCH v2 net-next 4/4] net: fib: avoid calling fib_flush for each device when doing batch close and unregister

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Message-ID: <56B4C7F2.1020109@cogentembedded.com>
Date:	Fri, 5 Feb 2016 19:04:02 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Salam Noureddine <noureddine@...sta.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jiri Pirko <jiri@...lanox.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Julian Anastasov <ja@....bg>, netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next 4/4] net: fib: avoid calling fib_flush for
 each device when doing batch close and unregister

On 02/05/2016 02:35 AM, Salam Noureddine wrote:

> Call fib_flush at the end when closing or unregistering multiple
> devices. This can save walking the fib many times and greatly
> reduce rtnl_lock hold time when unregistering many devices with
> a fib having hundreds of thousands of routes.
>
> Signed-off-by: Salam Noureddine <noureddine@...sta.com>
> ---
>   include/net/netns/ipv4.h |  1 +
>   net/ipv4/fib_frontend.c  | 16 ++++++++++++++--
>   2 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
> index d75be32..d59a078 100644
> --- a/include/net/netns/ipv4.h
> +++ b/include/net/netns/ipv4.h
[...]
> diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
> index 4734475..808426e 100644
> --- a/net/ipv4/fib_frontend.c
> +++ b/net/ipv4/fib_frontend.c
> @@ -1161,11 +1161,22 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
>   	unsigned int flags;
>
>   	if (event == NETDEV_UNREGISTER) {
> -		fib_disable_ip(dev, event, true);
> +		if (fib_sync_down_dev(dev, event, true))
> +			net->ipv4.needs_fib_flush = true;
>   		rt_flush_dev(dev);
>   		return NOTIFY_DONE;
>   	}
>
> +	if (event == NETDEV_UNREGISTER_BATCH || event == NETDEV_DOWN_BATCH) {
> +		if (net->ipv4.needs_fib_flush) {
> +			fib_flush(net);
> +			net->ipv4.needs_fib_flush = false;
> +		}
> +		rt_cache_flush(net);
> +		arp_ifdown_all();
> +		return NOTIFY_DONE;
> +	}
> +

    I'd convert to *switch* the above 2 *if*'s...

[...]

MBR, Sergei