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Date:   Fri, 10 Jul 2020 15:26:58 +0200
From:   Jesper Dangaard Brouer <brouer@redhat.com>
To:     Christoph Hellwig <hch@lst.de>
Cc:     iommu@lists.linux-foundation.org,
        Alexey Kardashevskiy <aik@ozlabs.ru>,
        linuxppc-dev@lists.ozlabs.org, Lu Baolu <baolu.lu@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Joerg Roedel <joro@8bytes.org>,
        Robin Murphy <robin.murphy@arm.com>,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@gmail.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        linux-kernel@vger.kernel.org, brouer@redhat.com
Subject: Re: generic DMA bypass flag v4
Message-ID: <20200710152658.31a9391a@carbon>
In-Reply-To: <20200708152449.316476-1-hch@lst.de>
References: <20200708152449.316476-1-hch@lst.de>
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On Wed,  8 Jul 2020 17:24:44 +0200
Christoph Hellwig <hch@lst.de> wrote:

> Note that as-is this breaks the XSK buffer pool, which unfortunately
> poked directly into DMA internals.  A fix for that is already queued
> up in the netdev tree.
>=20
> Jesper and XDP gang: this should not regress any performance as
> the dma-direct calls are now inlined into the out of line DMA mapping
> calls.  But if you can verify the performance numbers that would be
> greatly appreciated.

=46rom a superficial review of the patches, they look okay to me. I don't
have time to run a performance benchmark (before I go on vacation).

I hoped Bj=C3=B6rn could test/benchmark this(?), given (as mentioned) this
also affect XSK / AF_XDP performance.

--=20
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer