Messages in this thread | | | Subject | Re: [RFC PATCH v3 4/5] skb: add tracepoints to freeing skb | From | Eric Dumazet <> | Date | Tue, 20 Jul 2010 06:54:03 +0200 |
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Le mardi 20 juillet 2010 à 09:49 +0900, Koki Sanagi a écrit : > [RFC PATCH v3 4/5] skb: add tracepoints to freeing skb > This patch adds tracepoint to consume_skb, dev_kfree_skb_irq and > skb_free_datagram_locked. Combinating with tracepoint on dev_hard_start_xmit, > we can check how long it takes to free transmited packets. And using it, we can > calculate how many packets driver had at that time. It is useful when a drop of > transmited packet is a problem. > > <idle>-0 [001] 241409.218333: consume_skb: skbaddr=dd6b2fb8 > <idle>-0 [001] 241409.490555: dev_kfree_skb_irq: skbaddr=f5e29840 > > udp-recv-302 [001] 515031.206008: skb_free_datagram_locked: skbaddr=f5b1d900 > > > Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com> > --- > include/trace/events/skb.h | 42 ++++++++++++++++++++++++++++++++++++++++++ > net/core/datagram.c | 1 + > net/core/dev.c | 2 ++ > net/core/skbuff.c | 1 + > 4 files changed, 46 insertions(+), 0 deletions(-) > > diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h > index 4b2be6d..84c9041 100644 > --- a/include/trace/events/skb.h > +++ b/include/trace/events/skb.h > @@ -35,6 +35,48 @@ TRACE_EVENT(kfree_skb, > __entry->skbaddr, __entry->protocol, __entry->location) > ); > > +DECLARE_EVENT_CLASS(free_skb, > + > + TP_PROTO(struct sk_buff *skb), > + > + TP_ARGS(skb), > + > + TP_STRUCT__entry( > + __field( void *, skbaddr ) > + ), > + > + TP_fast_assign( > + __entry->skbaddr = skb; > + ), > + > + TP_printk("skbaddr=%p", __entry->skbaddr) > + > +); > + > +DEFINE_EVENT(free_skb, consume_skb, > + > + TP_PROTO(struct sk_buff *skb), > + > + TP_ARGS(skb) > + > +); > + > +DEFINE_EVENT(free_skb, dev_kfree_skb_irq, > + > + TP_PROTO(struct sk_buff *skb), > + > + TP_ARGS(skb) > + > +); > + > +DEFINE_EVENT(free_skb, skb_free_datagram_locked, > + > + TP_PROTO(struct sk_buff *skb), > + > + TP_ARGS(skb) > + > +); > + > TRACE_EVENT(skb_copy_datagram_iovec, > > TP_PROTO(const struct sk_buff *skb, int len), > diff --git a/net/core/datagram.c b/net/core/datagram.c > index f5b6f43..1ea32a0 100644 > --- a/net/core/datagram.c > +++ b/net/core/datagram.c > @@ -231,6 +231,7 @@ void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb) > { > bool slow; > > + trace_skb_free_datagram_locked(skb);
Here you unconditionally trace before the test on skb->users
> if (likely(atomic_read(&skb->users) == 1)) > smp_rmb(); > else if (likely(!atomic_dec_and_test(&skb->users))) > diff --git a/net/core/dev.c b/net/core/dev.c > index 4acfec6..d979847 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -131,6 +131,7 @@ > #include <linux/random.h> > #include <trace/events/napi.h> > #include <trace/events/net.h> > +#include <trace/events/skb.h> > #include <linux/pci.h> > > #include "net-sysfs.h" > @@ -1581,6 +1582,7 @@ void dev_kfree_skb_irq(struct sk_buff *skb) > struct softnet_data *sd; > unsigned long flags; > > + trace_dev_kfree_skb_irq(skb); > local_irq_save(flags); > sd = &__get_cpu_var(softnet_data); > skb->next = sd->completion_queue; > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 34432b4..a7b4036 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -466,6 +466,7 @@ void consume_skb(struct sk_buff *skb) > smp_rmb(); > else if (likely(!atomic_dec_and_test(&skb->users))) > return;
While here you trace _after_ the test on skb->users - and a "return;" , so you miss some consume_skb() calls
> + trace_consume_skb(skb); > __kfree_skb(skb); > } > EXPORT_SYMBOL(consume_skb); >
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