Thanks Jon, your explanation is very helpful.
One more question: in this definition,
TRACE_1(TR_FAC_IP, TR_IP_RPUT_START, "ip_input_start: q %p", q);
only "q" is an argument. Where does the "ip_input_start: q %p" stuff
go? Or, what is it used?
Thanks.
On Fri, May 30, 2008 at 7:28 PM, Jon Haslam <[EMAIL PROTECTED]> wrote:
>
>> The comments at the top of sys/vtrace.h explains the background, but
>> doesn't state in detail how to use it. In particular, what the type
>> and the format of the arguments are.
>>
>> For example, to monitor this (in uts/common/inet/ip/ip.c)
>> TRACE_1(TR_FAC_IP, TR_IP_RPUT_START, "ip_input_start: q %p", q);
>
> The digit given in the TRACE_?() macros specify how many arguments
> are being provided, so with TRACE_1() there is 1 argument. Unfortunately,
> the vtrace probes don't have their argument type information exported
> so you can't use the args[] array to access them or the '-v' flag
> to dtrace(1M). In this case you need to use the source to look at the
> arguments and then either use the source or mdb(1) to look at the types.
> Then you cast the arguments accordingly.
>
> So, with your example of vtrace:ip:ip_input:TR_IP_RPUT_START, this
> takes a single argument of a queue_t pointer as you state. To use
> this just do something like:
>
> vtrace:ip:ip_input:TR_IP_RPUT_START
> {
> this->queue = (queue_t *)arg0;
> printf("High Water = %d\n", this->queue->q_hiwat);
> }
>
> As I said, to find the definition of a queue_t, either use the
> source or mdb:
>
> # mdb -k
> Loading modules: [ unix genunix dtrace specfs ufs scsi_vhci sd isp pcisch
> sgsbbc ip hook neti sctp arp fctl nca lofs zfs random ipc sppp cpc ptm nfs
> fcip logindmux ]
>> ::print -t queue_t
> {
> struct qinit *q_qinfo
> struct msgb *q_first
> struct msgb *q_last
> struct queue *q_next
> struct queue *q_link
> <chop>
>
> Hope this helps.
>
> Jon.
>
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