netdev - Re: [PATCH net-next 03/11] ipv6/addrconf: switch to per netns inet6_addr

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Date:   Mon, 7 Feb 2022 20:12:15 -0800
From:   David Ahern <dsahern@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>, David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next 03/11] ipv6/addrconf: switch to per netns
 inet6_addr_lst hash table

On 2/7/22 9:17 AM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> IPv6 does not scale very well with the number of IPv6 addresses.
> It uses a global (shared by all netns) hash table with 256 buckets.
> 
> Some functions like addrconf_verify_rtnl() and addrconf_ifdown()
> have to iterate all addresses in the hash table.
> 
> I have seen addrconf_verify_rtnl() holding the cpu for 10ms or more.
> 
> Switch to the per netns hashtable (and spinlock) added
> in prior patches.
> 
> This considerably speeds up netns dismantle times on hosts
> with thousands of netns.

this has to speed up many aspects of ipv6 addresses, not just the teardown.

> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
>  net/ipv6/addrconf.c | 77 ++++++++++++++-------------------------------
>  1 file changed, 23 insertions(+), 54 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@...nel.org>