netdev - Re: [PATCH net-next v4 1/2] net: Add a second bind table hashed by port and address

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Message-ID: <CANn89iKryk30MM=XuwDmdZ7T_rDJUe+zZrZMsaPXQG2mghe6tQ@mail.gmail.com>
Date:   Tue, 17 May 2022 09:59:08 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Joanne Koong <joannelkoong@...il.com>
Cc:     netdev <netdev@...r.kernel.org>, Martin KaFai Lau <kafai@...com>,
        Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH net-next v4 1/2] net: Add a second bind table hashed by
 port and address

On Thu, May 12, 2022 at 1:51 PM Joanne Koong <joannelkoong@...il.com> wrote:
>
> We currently have one tcp bind table (bhash) which hashes by port
> number only. In the socket bind path, we check for bind conflicts by
> traversing the specified port's inet_bind2_bucket while holding the
> bucket's spinlock (see inet_csk_get_port() and inet_csk_bind_conflict()).
>
> In instances where there are tons of sockets hashed to the same port
> at different addresses, checking for a bind conflict is time-intensive
> and can cause softirq cpu lockups, as well as stops new tcp connections
> since __inet_inherit_port() also contests for the spinlock.
>
> This patch proposes adding a second bind table, bhash2, that hashes by
> port and ip address. Searching the bhash2 table leads to significantly
> faster conflict resolution and less time holding the spinlock.
>
> Signed-off-by: Joanne Koong <joannelkoong@...il.com>

Scary patch, but I could not find obvious issues with it.
Let's give it a try, thanks !

Reviewed-by: Eric Dumazet <edumazet@...gle.com>