From mboxrd@z Thu Jan  1 00:00:00 1970
From: Richard Cochran <richardcochran@gmail.com>
Subject: Re: [PATCH net-next 1/2] mlx4_en: Add PTP hardware clock
Date: Mon, 23 Dec 2013 19:48:46 +0100
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Cc: Shawn Bohrer <shawn.bohrer@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Or Gerlitz <ogerlitz@mellanox.com>,
	Amir Vadai <amirv@mellanox.com>, netdev@vger.kernel.org,
	tomk@rgmadvisors.com, Shawn Bohrer <sbohrer@rgmadvisors.com>
To: Hadar Hen Zion <hadarh@mellanox.com>
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On Sun, Dec 22, 2013 at 03:13:12PM +0200, Hadar Hen Zion wrote:

> 2. Adding spin lock in the data path reduce performance by 15% when
> HW timestamping is enabled. I did some testing and replacing
> spin_lock_irqsave with read/write_lock_irqsave prevents the
> performance decrease.

Why do the spin locks cause such a bottleneck?

Is there really that much lock contention in your test?

Your figure of 15% seems awfully high. How did you arrive at that
figure?

Thanks,
Richard