linux-kernel - Re: [PATCH net-next] net: mvpp2: Use relaxed I/O in data path

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Message-Id: <20180327.131624.64497520832369981.davem@davemloft.net>
Date:   Tue, 27 Mar 2018 13:16:24 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     maxime.chevallier@...tlin.com
Cc:     ymarkman@...vell.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, antoine.tenart@...tlin.com,
        thomas.petazzoni@...tlin.com, gregory.clement@...tlin.com,
        miquel.raynal@...tlin.com, nadavh@...vell.com, stefanc@...vell.com,
        mw@...ihalf.com
Subject: Re: [PATCH net-next] net: mvpp2: Use relaxed I/O in data path

From: Maxime Chevallier <maxime.chevallier@...tlin.com>
Date: Tue, 27 Mar 2018 16:49:05 +0200

> From: Yan Markman <ymarkman@...vell.com>
> 
> Use relaxed I/O on the hot path. This achieves significant performance
> improvements. On a 10G link, this makes a basic iperf TCP test go from
> an average of 4.5 Gbits/sec to about 9.40 Gbits/sec.
> 
> Signed-off-by: Yan Markman <ymarkman@...vell.com>
> [Maxime: Commit message, cosmetic changes]
> Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
> ---
> David, this patch should not conflict with other the pending PPv2 series I sent
> earlier ("[PATCH net-next 0/2] net: mvpp2: Remove unnecessary dynamic allocs")

Applied, but it is up to you to make sure the correct barriers are in place
such that undesirable memory and IOMEM operation reordering does not occur.

Said another way, you get to keep the pieces if this breaks things :-)