linux-kernel - Re: [PATCH 3/3] fm10k/igb/ixgbe: Use load

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Date:	Fri, 14 Nov 2014 09:25:19 -0800
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	Alexander Duyck <alexander.h.duyck@...hat.com>
Cc:	linux-arch@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, mikey@...ling.org,
	tony.luck@...el.com, mathieu.desnoyers@...ymtl.ca,
	donald.c.skidmore@...el.com, peterz@...radead.org,
	benh@...nel.crashing.org, heiko.carstens@...ibm.com,
	oleg@...hat.com, will.deacon@....com, davem@...emloft.net,
	michael@...erman.id.au, matthew.vick@...el.com,
	nic_swsd@...ltek.com, geert@...ux-m68k.org, fweisbec@...il.com,
	schwidefsky@...ibm.com, linux@....linux.org.uk,
	paulmck@...ux.vnet.ibm.com, torvalds@...ux-foundation.org,
	mingo@...nel.org
Subject: Re: [PATCH 3/3] fm10k/igb/ixgbe: Use load_acquire on Rx descriptor

On Thu, 2014-11-13 at 11:27 -0800, Alexander Duyck wrote:
> This change makes it so that load_acquire is used when reading the Rx
> descriptor.  The advantage of load_acquire is that it allows for a
> much
> lower cost barrier on x86, ia64, powerpc, arm64, and s390
> architectures
> than a traditional memory barrier when dealing with reads that only
> have
> to synchronize to system memory.
> 
> In addition I have updated the code so that it just checks to see if
> any
> bits have been set instead of just the DD bit since the DD bit will
> always
> be set as a part of a descriptor write-back so we just need to check
> for a
> non-zero value being present at that memory location rather than just
> checking for any specific bit.  This allows the code itself to appear
> much
> cleaner and allows the compiler more room to optimize.
> 
> Cc: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> Cc: Matthew Vick <matthew.vick@...el.com>
> Cc: Don Skidmore <donald.c.skidmore@...el.com>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...hat.com>
> ---
>  drivers/net/ethernet/intel/fm10k/fm10k_main.c |    8 +++-----
>  drivers/net/ethernet/intel/igb/igb_main.c     |    8 +++-----
>  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |   11 ++++-------
>  3 files changed, 10 insertions(+), 17 deletions(-)

Based on the discussion on patch 01 of the series, it appears changes
are coming to the series, so I won't be picking up this patch.  I will
wait for Alex to re-spin the series with the suggested changes.

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