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    SubjectRe: [ltt-dev] [PATCH] add tracepoints to track change in napi states on network receive
    On Wed, Dec 03, 2008 at 12:25:07PM -0500, Mathieu Desnoyers wrote:
    > Almost there :)
    >
    > There is a extra whitespace above,
    >
    > and also "schedule napi_struct" should probably be changed into
    > napi_struct only, this removes the whitespace and duplicated information
    > (I guess we know that given we are in event net_napi_schedule, this will
    > have something to do with schedule...). Same applies to trace_mark_tp
    > below.
    >
    > Thanks,
    >
    > Mathieu


    Sure, here you go, new patch

    Patch to trace napi states for various net devices and their napi instances.
    Traces scheduling, servicing and completion of a napi poll request.

    Regards
    Neil

    Signed-off-by: Neil Horman <nhorman@tuxdriver.com>


    include/linux/netdevice.h | 5 +++++
    include/trace/netdevice.h | 30 ++++++++++++++++++++++++++++++
    ltt/probes/net-trace.c | 22 ++++++++++++++++++++++
    net/core/dev.c | 7 ++++++-
    4 files changed, 63 insertions(+), 1 deletion(-)


    diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
    index 488c56e..7da71eb 100644
    --- a/include/linux/netdevice.h
    +++ b/include/linux/netdevice.h
    @@ -43,6 +43,9 @@

    #include <net/net_namespace.h>

    +struct napi_struct;
    +#include <trace/netdevice.h>
    +
    struct vlan_group;
    struct ethtool_ops;
    struct netpoll_info;
    @@ -386,6 +389,7 @@ static inline void napi_complete(struct napi_struct *n)
    local_irq_save(flags);
    __napi_complete(n);
    local_irq_restore(flags);
    + trace_napi_complete(n);
    }

    /**
    @@ -1726,6 +1730,7 @@ static inline int skb_bond_should_drop(struct sk_buff *skb)
    return 0;
    }

    +
    #endif /* __KERNEL__ */

    #endif /* _LINUX_DEV_H */
    diff --git a/include/trace/netdevice.h b/include/trace/netdevice.h
    new file mode 100644
    index 0000000..ba48f6c
    --- /dev/null
    +++ b/include/trace/netdevice.h
    @@ -0,0 +1,30 @@
    +#ifndef _INCLUDE_NETDEVICE_H_
    +#define _INCLUDE_NETDEVICE_H_
    +
    +#include <linux/netdevice.h>
    +
    +/* Tracepoints */
    +
    +/*
    + * Note these first 2 traces are actually in __napi_schedule and net_rx_action
    + * respectively. The former is in __napi_schedule because it uses at-most-once
    + * logic and placing it in the calling routine (napi_schedule) would produce
    + * countless trace events that were effectively no-ops. napi_poll is
    + * implemented in net_rx_action, because thats where we do our polling on
    + * devices. The last trace point is in napi_complete, right where you would
    + * think it would be.
    + */
    +DEFINE_TRACE(napi_schedule,
    + TPPROTO(struct napi_struct *n),
    + TPARGS(n));
    +
    +DEFINE_TRACE(napi_poll,
    + TPPROTO(struct napi_struct *n),
    + TPARGS(n));
    +
    +DEFINE_TRACE(napi_complete,
    + TPPROTO(struct napi_struct *n),
    + TPARGS(n));
    +
    +#endif
    +
    diff --git a/ltt/probes/net-trace.c b/ltt/probes/net-trace.c
    index bac2b21..e887e70 100644
    --- a/ltt/probes/net-trace.c
    +++ b/ltt/probes/net-trace.c
    @@ -9,6 +9,7 @@
    #include <trace/ipv4.h>
    #include <trace/ipv6.h>
    #include <trace/socket.h>
    +#include <trace/netdevice.h>

    void probe_net_dev_xmit(struct sk_buff *skb)
    {
    @@ -104,6 +105,27 @@ void probe_socket_call(int call, unsigned long a0)
    "call %d a0 %lu", call, a0);
    }

    +void probe_napi_schedule(struct napi_struct *n)
    +{
    + trace_mark_tp(net_napi_schedule, napi_schedule, probe_napi_schedule,
    + "napi_struct %p name %s",
    + n, n->dev->name);
    +}
    +
    +void probe_napi_poll(struct napi_struct *n)
    +{
    + trace_mark_tp(net_napi_poll, napi_poll, probe_napi_poll,
    + "napi_struct %p name %s",
    + n, n->dev->name);
    +}
    +
    +void probe_napi_complete(struct napi_struct *n)
    +{
    + trace_mark_tp(net_napi_complete, napi_complete, probe_napi_complete,
    + "napi_struct %p name %s",
    + n, n->dev->name);
    +}
    +
    MODULE_LICENSE("GPL");
    MODULE_AUTHOR("Mathieu Desnoyers");
    MODULE_DESCRIPTION("Net Tracepoint Probes");
    diff --git a/net/core/dev.c b/net/core/dev.c
    index 836fe6e..0c55c0f 100644
    --- a/net/core/dev.c
    +++ b/net/core/dev.c
    @@ -128,6 +128,7 @@
    #include <linux/jhash.h>
    #include <linux/random.h>
    #include <trace/net.h>
    +#include <trace/netdevice.h>

    #include "net-sysfs.h"

    @@ -2329,6 +2330,8 @@ void __napi_schedule(struct napi_struct *n)
    {
    unsigned long flags;

    + trace_napi_poll(n);
    +
    local_irq_save(flags);
    list_add_tail(&n->poll_list, &__get_cpu_var(softnet_data).poll_list);
    __raise_softirq_irqoff(NET_RX_SOFTIRQ);
    @@ -2380,8 +2383,10 @@ static void net_rx_action(struct softirq_action *h)
    * accidently calling ->poll() when NAPI is not scheduled.
    */
    work = 0;
    - if (test_bit(NAPI_STATE_SCHED, &n->state))
    + if (test_bit(NAPI_STATE_SCHED, &n->state)) {
    + trace_napi_poll(n);
    work = n->poll(n, weight);
    + }

    WARN_ON_ONCE(work > weight);

    --
    /****************************************************
    * Neil Horman <nhorman@tuxdriver.com>
    * Software Engineer, Red Hat
    ****************************************************/

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