From: Jeff.Haran@citrix.com (Jeff Haran)
To: kernelnewbies@lists.kernelnewbies.org
Subject: Regarding skb and skb_frags
Date: Thu, 1 May 2014 16:20:47 +0000 [thread overview]
Message-ID: <4E5779AD88B2F040B8A7E83ECF544D1A508E7B@SJCPEX01CL02.citrite.net> (raw)
In-Reply-To: <CA+aCy1GsXFzg=BJMdyXyr7DX5aFccQWpkZoxkv+XTZKwaWc8dQ@mail.gmail.com>
> -----Original Message-----
> From: kernelnewbies-bounces at kernelnewbies.org [mailto:kernelnewbies-bounces at kernelnewbies.org] On Behalf Of Pranay
> Srivastava
> Sent: Thursday, May 01, 2014 7:10 AM
> To: Valdis.Kletnieks at vt.edu
> Cc: kernelnewbies
> Subject: Re: Regarding skb and skb_frags
>
> On Thu, May 1, 2014 at 7:29 PM, <Valdis.Kletnieks@vt.edu> wrote:
> > On Thu, 01 May 2014 16:12:43 +0530, Pranay Srivastava said:
> >
> >> My question is that an Ethernet frame won't be bigger than 1500 bytes
> >> [correct?]
> >
> > Incorrect. 10G and faster ethernet support jumbograms. We run our HPC 10G
> > network with an MTU of 9000 (which is 2 pages and a bit more).
> >
> Ok. So in any case the driver won't poke past ethernet header to look
> for the size [Correct?].
> So it means only when MTU is bigger than page size would there be a
> possibility of skb_frags [Correct?].
I'm not sure what kernel version you are looking at, but when I do a search for skb_frags in the latest kernel sources at http://lxr.linux.no, I don't see any variables or structure members named skb_frags, though it shows up in comments in one driver.
That being said, I believe skb fragments are also used to implement scatter/gather lists of packet payload data, even in packets less than or equal to the usual 1500 bytes.
On the systems I work with, I've seen this happening in packets originating from the target system, i.e. egress path of local traffic.
Jeff Haran
next prev parent reply other threads:[~2014-05-01 16:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-01 10:42 Regarding skb and skb_frags Pranay Srivastava
2014-05-01 13:59 ` Valdis.Kletnieks at vt.edu
2014-05-01 14:09 ` Pranay Srivastava
2014-05-01 16:20 ` Jeff Haran [this message]
2014-05-02 3:16 ` Pranay Srivastava
2014-05-02 16:21 ` Jeff Haran
2014-05-13 3:04 ` Li Wei
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