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Message-ID: <CAL+tcoDnRmORP9UKg7k3grB0zaThY7V964pAfY=NuZu33-WkoQ@mail.gmail.com>
Date: Mon, 9 Dec 2024 22:57:01 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, dsahern@...nel.org, willemb@...gle.com, ast@...nel.org,
daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev,
eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev,
john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me,
haoluo@...gle.com, jolsa@...nel.org, bpf@...r.kernel.org,
netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v4 03/11] net-timestamp: reorganize in skb_tstamp_tx_output()
On Mon, Dec 9, 2024 at 10:37 PM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> Jason Xing wrote:
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > It's a prep for bpf print function later. This patch only puts the
> > original generating logic into one function, so that we integrate
> > bpf print easily. No functional changes here.
> >
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > ---
> > include/linux/skbuff.h | 4 ++--
> > net/core/dev.c | 3 +--
> > net/core/skbuff.c | 41 +++++++++++++++++++++++++++++++++++------
> > 3 files changed, 38 insertions(+), 10 deletions(-)
> >
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index 58009fa66102..53c6913560e4 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -39,6 +39,7 @@
> > #include <net/net_debug.h>
> > #include <net/dropreason-core.h>
> > #include <net/netmem.h>
> > +#include <uapi/linux/errqueue.h>
> >
> > /**
> > * DOC: skb checksums
> > @@ -4535,8 +4536,7 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
> > static inline void skb_tx_timestamp(struct sk_buff *skb)
> > {
> > skb_clone_tx_timestamp(skb);
> > - if (skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP)
> > - skb_tstamp_tx(skb, NULL);
> > + __skb_tstamp_tx(skb, NULL, NULL, skb->sk, SCM_TSTAMP_SND);
> > }
> >
> > /**
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index 45a8c3dd4a64..5d584950564b 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -4350,8 +4350,7 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
> > skb_reset_mac_header(skb);
> > skb_assert_len(skb);
> >
> > - if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP))
> > - __skb_tstamp_tx(skb, NULL, NULL, skb->sk, SCM_TSTAMP_SCHED);
> > + __skb_tstamp_tx(skb, NULL, NULL, skb->sk, SCM_TSTAMP_SCHED);
>
> This adds a function call in the hot path, as __skb_tstamp_tx is
> defined in a .c file.
>
> Currently this is only well predicted branch on a likely cache hot
> variable.
Oh, right, thanks for reminding me. I will figure out a better solution :)
> >
> > /* Disable soft irqs for various locks below. Also
> > * stops preemption for RCU.
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index 6841e61a6bd0..74b840ffaf94 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -5539,10 +5539,10 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
> > }
> > EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);
> >
> > -void __skb_tstamp_tx(struct sk_buff *orig_skb,
> > - const struct sk_buff *ack_skb,
> > - struct skb_shared_hwtstamps *hwtstamps,
> > - struct sock *sk, int tstype)
> > +static void skb_tstamp_tx_output(struct sk_buff *orig_skb,
> > + const struct sk_buff *ack_skb,
> > + struct skb_shared_hwtstamps *hwtstamps,
> > + struct sock *sk, int tstype)
> > {
> > struct sk_buff *skb;
> > bool tsonly, opt_stats = false;
> > @@ -5594,13 +5594,42 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
> >
> > __skb_complete_tx_timestamp(skb, sk, tstype, opt_stats);
> > }
> > +
> > +static bool skb_tstamp_is_set(const struct sk_buff *skb, int tstype)
> > +{
> > + switch (tstype) {
> > + case SCM_TSTAMP_SCHED:
> > + if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP))
> > + return true;
> > + return false;
> > + case SCM_TSTAMP_SND:
> > + if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP))
> > + return true;
>
> Also true for SKBTX_HW_TSTAMP
>
> > + return false;
> > + case SCM_TSTAMP_ACK:
> > + if (TCP_SKB_CB(skb)->txstamp_ack)
> > + return true;
> > + return false;
> > + }
> > +
> > + return false;
> > +}
> > +
> > +void __skb_tstamp_tx(struct sk_buff *orig_skb,
> > + const struct sk_buff *ack_skb,
> > + struct skb_shared_hwtstamps *hwtstamps,
> > + struct sock *sk, int tstype)
> > +{
> > + if (unlikely(skb_tstamp_is_set(orig_skb, tstype)))
> > + skb_tstamp_tx_output(orig_skb, ack_skb, hwtstamps, sk, tstype);
> > +}
> > EXPORT_SYMBOL_GPL(__skb_tstamp_tx);
> >
> > void skb_tstamp_tx(struct sk_buff *orig_skb,
> > struct skb_shared_hwtstamps *hwtstamps)
> > {
> > - return __skb_tstamp_tx(orig_skb, NULL, hwtstamps, orig_skb->sk,
> > - SCM_TSTAMP_SND);
> > + return skb_tstamp_tx_output(orig_skb, NULL, hwtstamps, orig_skb->sk,
> > + SCM_TSTAMP_SND);
> > }
> > EXPORT_SYMBOL_GPL(skb_tstamp_tx);
> >
> > --
> > 2.37.3
> >
>
>
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