From: Rusty Russell <rusty@rustcorp•com.au>
To: Michael Dalton <mwdalton@google•com>,
"David S. Miller" <davem@davemloft•net>
Cc: netdev@vger•kernel.org, Eric Dumazet <edumazet@google•com>,
"Michael S. Tsirkin" <mst@redhat•com>,
Daniel Borkmann <dborkman@redhat•com>,
virtualization@lists•linux-foundation.org,
Michael Dalton <mwdalton@google•com>
Subject: Re: [PATCH net-next] virtio_net: migrate mergeable rx buffers to page frag allocators
Date: Tue, 29 Oct 2013 12:21:56 +1030 [thread overview]
Message-ID: <87ppqoetdv.fsf@rustcorp.com.au> (raw)
In-Reply-To: <1383000258-1458-1-git-send-email-mwdalton@google.com>
Michael Dalton <mwdalton@google•com> writes:
> The virtio_net driver's mergeable receive buffer allocator
> uses 4KB packet buffers. For MTU-sized traffic, SKB truesize
> is > 4KB but only ~1500 bytes of the buffer is used to store
> packet data, reducing the effective TCP window size
> substantially. This patch addresses the performance concerns
> with mergeable receive buffers by allocating MTU-sized packet
> buffers using page frag allocators. If more than MAX_SKB_FRAGS
> buffers are needed, the SKB frag_list is used.
>
> Signed-off-by: Michael Dalton <mwdalton@google•com>
Hi Michael,
Nice work! Just one comment. Your patch highlights the
anachronistic name MAX_PACKET_LEN: it was from the original
implementation which only supported 1500 byte packets, and only used in
one place.
Please apply a first patch like this, then come up with a new constant
name (GOOD_PACKET_LEN?) for that value. Because it's not the maximum
packet we can receive for mergable buffers.
Thanks,
Rusty.
Subject: virtio_net: remove anachronistic MAX_PACKET_LEN constant.
From: Rusty Russell <rusty@rustcorp•com.au>
The initial implementation of virtio_net only allowed ethernet-style
MTU packets; with more recent features this isn't true. Move the
constant into the function where it's used.
Signed-off-by: Rusty Russell <rusty@rustcorp•com.au>
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 057ea13..dcbfccd 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -35,8 +35,6 @@ static bool csum = true, gso = true;
module_param(csum, bool, 0444);
module_param(gso, bool, 0444);
-/* FIXME: MTU in config. */
-#define MAX_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
#define GOOD_COPY_LEN 128
#define VIRTNET_DRIVER_VERSION "1.0.0"
@@ -434,12 +432,13 @@ static int add_recvbuf_small(struct receive_queue *rq, gfp_t gfp)
struct sk_buff *skb;
struct skb_vnet_hdr *hdr;
int err;
+ const int len = ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN;
- skb = __netdev_alloc_skb_ip_align(vi->dev, MAX_PACKET_LEN, gfp);
+ skb = __netdev_alloc_skb_ip_align(vi->dev, len, gfp);
if (unlikely(!skb))
return -ENOMEM;
- skb_put(skb, MAX_PACKET_LEN);
+ skb_put(skb, len);
hdr = skb_vnet_hdr(skb);
sg_set_buf(rq->sg, &hdr->hdr, sizeof hdr->hdr);
next prev parent reply other threads:[~2013-10-29 1:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-28 22:44 [PATCH net-next] virtio_net: migrate mergeable rx buffers to page frag allocators Michael Dalton
2013-10-28 23:19 ` Eric Dumazet
2013-10-29 3:57 ` David Miller
2013-10-29 19:12 ` Michael S. Tsirkin
2013-10-29 7:30 ` Daniel Borkmann
2013-10-29 1:51 ` Rusty Russell [this message]
2013-10-29 6:27 ` Jason Wang
2013-10-29 18:44 ` Eric Northup
2013-10-29 19:05 ` Michael Dalton
2013-10-29 19:17 ` Michael S. Tsirkin
2013-10-30 4:41 ` Jason Wang
2013-10-29 19:05 ` Michael S. Tsirkin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87ppqoetdv.fsf@rustcorp.com.au \
--to=rusty@rustcorp$(echo .)com.au \
--cc=davem@davemloft$(echo .)net \
--cc=dborkman@redhat$(echo .)com \
--cc=edumazet@google$(echo .)com \
--cc=mst@redhat$(echo .)com \
--cc=mwdalton@google$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
--cc=virtualization@lists$(echo .)linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox