linux-kernel - Re: [PATCH 02/16] hyper-v: trace vmbus_on

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Date:   Thu, 21 Sep 2017 10:17:18 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     devel@...uxdriverproject.org, linux-kernel@...r.kernel.org,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>
Subject: Re: [PATCH 02/16] hyper-v: trace vmbus_on_message()

Steven Rostedt <rostedt@...dmis.org> writes:

> On Wed, 20 Sep 2017 19:21:53 +0200
> Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
>
>> diff --git a/drivers/hv/hv_trace.h b/drivers/hv/hv_trace.h
>> index 9a29ef55477d..72911dfc9682 100644
>> --- a/drivers/hv/hv_trace.h
>> +++ b/drivers/hv/hv_trace.h
>> @@ -14,6 +14,14 @@ TRACE_EVENT(vmbus_on_msg_dpc,
>>  	    TP_printk("message %u received", __entry->msgtype)
>>  	);
>>  
>> +TRACE_EVENT(vmbus_on_message,
>> +	    TP_PROTO(const struct vmbus_channel_message_header *hdr),
>> +	    TP_ARGS(hdr),
>> +	    TP_STRUCT__entry(__field(unsigned int, msgtype)),
>> +	    TP_fast_assign(__entry->msgtype = hdr->msgtype),
>> +	    TP_printk("processing message %u", __entry->msgtype)
>> +	);
>
> Whenever you have two trace events with everything the same but the
> TP_printk(), you can save a little space by using DEFINE_EVENT_PRINT()
>
> DECLARE_EVENT_CLASS(vmbus_hdr_msg,
> 	TP_PROTO(const struct vmbus_channel_message_header *hdr),
> 	TP_ARGS(hdr),
> 	TP_STRUCT__entry(__field(unsigned int, msgtype),
> 	TP_fast_assign(__entry->msg = hdr->msgtype;),
> 	TP_printk("msgtype=%d", __entry->msgtype)
> );
>
> DEFINE_EVENT_PRINT(vmbus_hdr_msg, vmbus_on_msg_dpc,
> 	TP_PROTO(const struct vmbus_channel_message_header *hdr),
> 	TP_ARGS(hdr),
> 	TP_printk("message %u received", __entry->msgtype));
>
> DEFINE_EVENT_PRINT(vmbus_hdr_msg, vmbus_on_message,
> 	TP_PROTO(const struct vmbus_channel_message_header *hdr),
> 	TP_ARGS(hdr),
> 	TP_printk("processing message %u", __entry->msgtype));
>
> This will use the same functions required to save and record the
> message but will use a different function to output it to the trace.

Oh, thanks! This seems to be useful for
vmbus_on_msg_dpc/vmbus_on_message only as all the rest needs to parse
different structures. Will use it in v2.

-- 
  Vitaly