netdev - Re: [PATCH v2 2/2] sctp: delay calls to sk_data

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Date:	Thu, 7 Apr 2016 10:35:25 -0300
From:	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:	Jakub Sitnicki <jkbs@...hat.com>
Cc:	netdev@...r.kernel.org, Neil Horman <nhorman@...driver.com>,
	Vlad Yasevich <vyasevich@...il.com>, linux-sctp@...r.kernel.org
Subject: Re: [PATCH v2 2/2] sctp: delay calls to sk_data_ready() as much as
 possible

On Thu, Apr 07, 2016 at 10:05:32AM +0200, Jakub Sitnicki wrote:
> On Wed, Apr 06, 2016 at 07:53 PM CEST, Marcelo Ricardo Leitner <marcelo.leitner@...il.com> wrote:
> > Currently, the processing of multiple chunks in a single SCTP packet
> > leads to multiple calls to sk_data_ready, causing multiple wake up
> > signals which are costly and doesn't make it wake up any faster.
> >
> > With this patch it will notice that the wake up is pending and will do it
> > before leaving the state machine interpreter, latest place possible to
> > do it realiably and cleanly.
> >
> > Note that sk_data_ready events are not dependent on asocs, unlike waking
> > up writers.
> >
> > Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> > ---
> 
> [...]
> 
> > diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
> > index 7fe56d0acabf66cfd8fe29dfdb45f7620b470ac7..e7042f9ce63b0cfca50cae252f51b60b68cb5731 100644
> > --- a/net/sctp/sm_sideeffect.c
> > +++ b/net/sctp/sm_sideeffect.c
> > @@ -1742,6 +1742,11 @@ out:
> >  			error = sctp_outq_uncork(&asoc->outqueue, gfp);
> >  	} else if (local_cork)
> >  		error = sctp_outq_uncork(&asoc->outqueue, gfp);
> > +
> > +	if (sctp_sk(ep->base.sk)->pending_data_ready) {
> > +		ep->base.sk->sk_data_ready(ep->base.sk);
> > +		sctp_sk(ep->base.sk)->pending_data_ready = 0;
> > +	}
> >  	return error;
> >  nomem:
> >  	error = -ENOMEM;
> 
> Would it make sense to introduce a local variable for ep->base.sk (and
> make this function 535+1 lines long ;-)
> 
>       struct sock *sk = ep->base.sk;
> 
> ... like sctp_ulpq_tail_event() does?

I guess so, yes. Same for sctp_sk() cast then. I´ll post a new version
later, thanks.

  Marcelo