From: "Michael S. Tsirkin" <mst@redhat.com>
To: David Miller <davem@davemloft.net>
Cc: john.fastabend@gmail.com, brouer@redhat.com, shrijeet@gmail.com,
tom@herbertland.com, netdev@vger.kernel.org,
shm@cumulusnetworks.com, roopa@cumulusnetworks.com,
nikolay@cumulusnetworks.com
Subject: Re: [PATCH net-next RFC WIP] Patch for XDP support for virtio_net
Date: Fri, 28 Oct 2016 01:25:48 +0300 [thread overview]
Message-ID: <20161028011739-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20161027.174218.654961317277160121.davem@davemloft.net>
On Thu, Oct 27, 2016 at 05:42:18PM -0400, David Miller wrote:
> From: "Michael S. Tsirkin" <mst@redhat.com>
> Date: Fri, 28 Oct 2016 00:30:35 +0300
>
> > Something I'd like to understand is how does XDP address the
> > problem that 100Byte packets are consuming 4K of memory now.
>
> Via page pools. We're going to make a generic one, but right now
> each and every driver implements a quick list of pages to allocate
> from (and thus avoid the DMA man/unmap overhead, etc.)
So to clarify, ATM virtio doesn't attempt to avoid dma map/unmap
so there should be no issue with that even when using sub/page
regions, assuming DMA APIs support sub-page map/unmap correctly.
The only reason virtio attempts to use sub-page fragments is to conserve
memory so that truesize for a 100byte packets won't be 4K. Are you
saying pools will somehow mean we won't need to worry about that so
effectively truesize=100byte even though the rest of the 4k page goes
unused? If so we'll happily go back to allocate memory in 4K chunks like
we used to before 2613af0ed18a, and remove a bunch of complexity.
--
MST
next prev parent reply other threads:[~2016-10-27 22:25 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-22 4:07 [PATCH net-next RFC WIP] Patch for XDP support for virtio_net Shrijeet Mukherjee
2016-10-23 16:38 ` Stephen Hemminger
2016-10-24 1:51 ` Shrijeet Mukherjee
2016-10-25 1:10 ` Alexei Starovoitov
2016-10-25 17:36 ` Jakub Kicinski
2016-10-26 13:52 ` Jesper Dangaard Brouer
2016-10-26 16:36 ` Michael S. Tsirkin
2016-10-26 16:52 ` David Miller
2016-10-26 17:07 ` Michael S. Tsirkin
2016-10-26 17:11 ` David Miller
2016-10-27 8:55 ` Jesper Dangaard Brouer
2016-10-27 21:09 ` John Fastabend
2016-10-27 21:30 ` Michael S. Tsirkin
2016-10-27 21:42 ` David Miller
2016-10-27 22:25 ` Michael S. Tsirkin [this message]
2016-10-28 1:35 ` David Miller
2016-10-28 1:43 ` Alexander Duyck
2016-10-28 2:10 ` David Miller
2016-10-28 15:56 ` John Fastabend
2016-10-28 16:18 ` Jakub Kicinski
2016-10-28 18:22 ` Alexei Starovoitov
2016-10-28 20:35 ` Alexander Duyck
2016-10-28 20:42 ` Jakub Kicinski
2016-10-28 20:36 ` Jakub Kicinski
2016-10-29 3:51 ` Shrijeet Mukherjee
2016-10-29 11:25 ` Thomas Graf
2016-11-02 14:27 ` Jesper Dangaard Brouer
2016-11-03 1:28 ` Shrijeet Mukherjee
2016-11-03 4:11 ` Michael S. Tsirkin
2016-11-03 6:44 ` John Fastabend
2016-11-03 22:20 ` John Fastabend
2016-11-03 22:42 ` Michael S. Tsirkin
2016-11-03 23:29 ` John Fastabend
2016-11-04 0:34 ` Michael S. Tsirkin
2016-11-04 23:05 ` John Fastabend
2016-11-06 6:50 ` Michael S. Tsirkin
2016-10-28 17:11 ` David Miller
2016-10-30 22:53 ` Michael S. Tsirkin
2016-11-02 14:01 ` Jesper Dangaard Brouer
2016-11-02 16:06 ` Alexander Duyck
2016-10-28 0:02 ` Shrijeet Mukherjee
2016-10-28 0:46 ` Shrijeet Mukherjee
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