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Date:   Thu, 17 Sep 2020 17:02:03 -0700
From:   Stephen Hemminger <stephen@networkplumber.org>
To:     fruggeri@arista.com (Francesco Ruggeri)
Cc:     linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        xiyou.wangcong@gmail.com, ap420073@gmail.com, andriin@fb.com,
        edumazet@google.com, jiri@mellanox.com, ast@kernel.org,
        kuba@kernel.org, davem@davemloft.net
Subject: Re: [PATCH v3] net: use exponential backoff in netdev_wait_allrefs
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On Thu, 17 Sep 2020 16:49:53 -0700
fruggeri@arista.com (Francesco Ruggeri) wrote:

> The combination of aca_free_rcu, introduced in commit 2384d02520ff
> ("net/ipv6: Add anycast addresses to a global hashtable"), and
> fib6_info_destroy_rcu, introduced in commit 9b0a8da8c4c6 ("net/ipv6:
> respect rcu grace period before freeing fib6_info"), can result in
> an extra rcu grace period being needed when deleting an interface,
> with the result that netdev_wait_allrefs ends up hitting the msleep(250),
> which is considerably longer than the required grace period.
> This can result in long delays when deleting a large number of interfaces,
> and it can be observed with this script:
> 

Is there anyway to make RCU trigger faster?