netdev - Re: [net-next PATCH] pktgen: add flag NO_TIMESTAMP to disable timestamping

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Message-ID: <1409329026.3173.93.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 29 Aug 2014 09:17:06 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Ben Greear <greearb@...delatech.com>,
	Robert Olsson <robert@...julf.se>
Subject: Re: [net-next PATCH] pktgen: add flag NO_TIMESTAMP to disable
 timestamping

On Thu, 2014-08-28 at 18:14 +0200, Jesper Dangaard Brouer wrote:
> Then testing the TX limits of the stack, then it is useful to
> be-able to disable the do_gettimeofday() timetamping on every packet.
> 
> This implements a pktgen flag NO_TIMESTAMP which will disable this
> call to do_gettimeofday().
> 
> The performance change on (my system E5-2695) with skb_clone=0, goes
> from TX 2,423,751 pps to 2,567,165 pps with flag NO_TIMESTAMP. Thus,
> the cost of do_gettimeofday() or saving is approx 23 nanosec.

I guess using local_clock() would provide an accurate and less expensive
timestamp, if a timestamp is needed.



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