linux-kernel - Re: [PATCH v3 net-next] udp: introduce __sk_mem

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Date:   Wed, 8 Mar 2023 10:12:51 +0800
From:   Jason Xing <kerneljasonxing@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     simon.horman@...igine.com, willemdebruijn.kernel@...il.com,
        davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com,
        kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH v3 net-next] udp: introduce __sk_mem_schedule() usage

On Tue, Mar 7, 2023 at 10:55 PM Paolo Abeni <pabeni@...hat.com> wrote:
>
> On Tue, 2023-03-07 at 09:56 +0800, Jason Xing wrote:
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > Keep the accounting schema consistent across different protocols
> > with __sk_mem_schedule(). Besides, it adjusts a little bit on how
> > to calculate forward allocated memory compared to before. After
> > applied this patch, we could avoid receive path scheduling extra
> > amount of memory.
> >
> > Link: https://lore.kernel.org/lkml/20230221110344.82818-1-kerneljasonxing@gmail.com/
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > ---
> > v3:
> > 1) get rid of inline suggested by Simon Horman
> >
> > v2:
> > 1) change the title and body message
> > 2) use __sk_mem_schedule() instead suggested by Paolo Abeni
> > ---
> >  net/ipv4/udp.c | 31 ++++++++++++++++++-------------
> >  1 file changed, 18 insertions(+), 13 deletions(-)
> >
> > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> > index c605d171eb2d..60473781933c 100644
> > --- a/net/ipv4/udp.c
> > +++ b/net/ipv4/udp.c
> > @@ -1531,10 +1531,23 @@ static void busylock_release(spinlock_t *busy)
> >               spin_unlock(busy);
> >  }
> >
> > +static int udp_rmem_schedule(struct sock *sk, int size)
> > +{
> > +     int delta;
> > +
> > +     delta = size - sk->sk_forward_alloc;
> > +     if (delta > 0 && !__sk_mem_schedule(sk, delta, SK_MEM_RECV))
> > +             return -ENOBUFS;
> > +
> > +     sk->sk_forward_alloc -= size;
>
> I think it's better if you maintain the above statement outside of this
> helper: it's a bit confusing that rmem_schedule() actually consumes fwd
> memory.

It does make sense.

Thanks,
Jason

>
> Side note
>
> Cheers,
>
> Paolo
>