Re: AF_XDP and dma
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- Subject: Re: AF_XDP and dma
- From: ratheesh kannoth <ratheesh.ksz@xxxxxxxxx>
- Date: Fri, 9 Apr 2021 16:53:35 +0530
- In-reply-to: <CAJ8uoz3ZoCXK6H7rrbV8oRA7TBBz9_zW=Um1+v4vNTXOWag8nw@mail.gmail.com>
- References: <CAGZFCEHR2brK5yoMZt=GsaZtg_0XB+sb-XLz_m5WjZr9xQDP3A@mail.gmail.com> <CAJ8uoz2Kv7aQP1BoxKET+v5k9jgSgQCK38RpNp-xCzwfEKvFRA@mail.gmail.com> <CAGZFCEGDtF1SfBWEbrYG9=Na+71mJ1kk5L+9W3f-UcKjYGjLCw@mail.gmail.com> <CAJ8uoz0O2yXoA09ZNO5iviFOv-ipgaf0ZhYD=ZUb8QG7VP5Edg@mail.gmail.com> <CAGZFCEEG=r1i4PY7bT3KOTEwR1RTMeqyS31fZ+kYp_XyvaH61w@mail.gmail.com> <CAJ8uoz3ipXOE2VeMLh02R0FKysuovLf3vFU_z5nEOffHNps1=g@mail.gmail.com> <CAGZFCEGzm5M=pnuXrA5vXGfntX8BOtyVfVK2hmANVfAn7b79=Q@mail.gmail.com> <CAJ8uoz3ZoCXK6H7rrbV8oRA7TBBz9_zW=Um1+v4vNTXOWag8nw@mail.gmail.com>
On Fri, Apr 9, 2021 at 4:36 PM Magnus Karlsson
<magnus.karlsson@xxxxxxxxx> wrote:
> In XDP/AF_XDP mode, the NIC only uses a single 4K page (on x86-64) per
> packet so it will be physically contiguous by definition.
How ? if userspace allocates memory, it would be only contiguous in
virtual address space.
>Every single
> page will be dma mapped separately and can reside anywhere.
I agree. My concern is not on total memory. it is about each chunk.
>There is
> no scatter-gather in XDP/AF_XDP mode.
i agree. i am not talking about Scatter gather (nr_frags or frag_list)
> > > > > > > /Magnus
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