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

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Date:   Wed, 20 Sep 2017 13:55:03 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
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()

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.

-- Steve