linux-kernel - Re: [PATCH RESEND net-next 1/2] dpaa2-eth: send a scatter-gather FD instead of realloc-ing

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Message-ID: <20201211093856.gj3do6ntnmxsqtzp@skbuf>
Date:   Fri, 11 Dec 2020 09:38:57 +0000
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     David Laight <David.Laight@...LAB.COM>
CC:     'Daniel Thompson' <daniel.thompson@...aro.org>,
        "linux-netdev@...r.kernel.org" <linux-netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND net-next 1/2] dpaa2-eth: send a scatter-gather FD
 instead of realloc-ing

On Fri, Dec 11, 2020 at 09:30:43AM +0000, David Laight wrote:
> From: Daniel Thompson
> > Sent: 10 December 2020 17:32
> > 
> > On Mon, Jun 29, 2020 at 06:47:11PM +0000, Ioana Ciornei wrote:
> > > Instead of realloc-ing the skb on the Tx path when the provided headroom
> > > is smaller than the HW requirements, create a Scatter/Gather frame
> > > descriptor with only one entry.
> 
> Is it worth simplifying the code by permanently allocating (and dma-mapping)
> the extra structure for every ring entry.
> It is (probably) only one page and 1 iommu entry.


That is exactly what I was thinking. At the moment the SGT structure is
pre-allocated but not pre-mapped.

I'll let you know how it goes.

Ioana