linux-kernel - Re: [PATCH net-next 3/5] net: napi: Make gro_flush

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Message-ID: <CANn89iJgXsn7yjWaiuuq=LFsKpQi8RQFo89MDRxeNddxeZUC2A@mail.gmail.com>
Date: Thu, 29 Aug 2024 17:31:30 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Joe Damato <jdamato@...tly.com>, Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org, 
	amritha.nambiar@...el.com, sridhar.samudrala@...el.com, sdf@...ichev.me, 
	bjorn@...osinc.com, hch@...radead.org, willy@...radead.org, 
	willemdebruijn.kernel@...il.com, skhawaja@...gle.com, kuba@...nel.org, 
	Martin Karsten <mkarsten@...terloo.ca>, "David S. Miller" <davem@...emloft.net>, 
	Paolo Abeni <pabeni@...hat.com>, Jiri Pirko <jiri@...nulli.us>, 
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Lorenzo Bianconi <lorenzo@...nel.org>, 
	Breno Leitao <leitao@...ian.org>, Johannes Berg <johannes.berg@...el.com>, 
	Alexander Lobakin <aleksander.lobakin@...el.com>, Heiner Kallweit <hkallweit1@...il.com>, 
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 3/5] net: napi: Make gro_flush_timeout per-NAPI

On Thu, Aug 29, 2024 at 5:28 PM Joe Damato <jdamato@...tly.com> wrote:
>
> On Thu, Aug 29, 2024 at 03:48:05PM +0200, Eric Dumazet wrote:
> > On Thu, Aug 29, 2024 at 3:13 PM Joe Damato <jdamato@...tly.com> wrote:
> > >
> > > Allow per-NAPI gro_flush_timeout setting.
> > >
> > > The existing sysfs parameter is respected; writes to sysfs will write to
> > > all NAPI structs for the device and the net_device gro_flush_timeout
> > > field.  Reads from sysfs will read from the net_device field.
> > >
> > > The ability to set gro_flush_timeout on specific NAPI instances will be
> > > added in a later commit, via netdev-genl.
> > >
> > > Signed-off-by: Joe Damato <jdamato@...tly.com>
> > > Reviewed-by: Martin Karsten <mkarsten@...terloo.ca>
> > > Tested-by: Martin Karsten <mkarsten@...terloo.ca>
> > > ---
> > >  include/linux/netdevice.h | 26 ++++++++++++++++++++++++++
> > >  net/core/dev.c            | 32 ++++++++++++++++++++++++++++----
> > >  net/core/net-sysfs.c      |  2 +-
> > >  3 files changed, 55 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > > index 7d53380da4c0..d00024d9f857 100644
> > > --- a/include/linux/netdevice.h
> > > +++ b/include/linux/netdevice.h
> > > @@ -372,6 +372,7 @@ struct napi_struct {
> > >         int                     rx_count; /* length of rx_list */
> > >         unsigned int            napi_id;
> > >         int                     defer_hard_irqs;
> > > +       unsigned long           gro_flush_timeout;
> > >         struct hrtimer          timer;
> > >         struct task_struct      *thread;
> > >         /* control-path-only fields follow */
> > > @@ -557,6 +558,31 @@ void napi_set_defer_hard_irqs(struct napi_struct *n, int defer);
> > >   */
> > >  void netdev_set_defer_hard_irqs(struct net_device *netdev, int defer);
> > >
> >
> > Same remark :  dev->gro_flush_timeout is no longer read in the fast path.
> >
> > Please move gro_flush_timeout out of net_device_read_txrx and update
> > Documentation/networking/net_cachelines/net_device.rst
>
> Is there some tooling I should use to generate this file?
>
> I am asking because it seems like the file is missing two fields in
> net_device at the end of the struct:
>
> struct hlist_head          page_pools;
> struct dim_irq_moder *     irq_moder;
>

At first glance this is control path only, no big deal.

> Both of which seem to have been added just before and long after
> (respectively) commit 14006f1d8fa2 ("Documentations: Analyze heavily
> used Networking related structs").
>
> If this is a bug, I can submit one patch (with two fixes tags) which
> adds both fields to the file?

No need for a Fixes: tag for this, just submit to net-next.

This file is really 'needed' for current development, for people
caring about data locality.