lkml.org 
[lkml]   [2016]   [Jan]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [BUG] skb corruption and kernel panic at forwarding with fragmentation
From
On Thu, Jan 7, 2016 at 2:35 PM, Konstantin Khlebnikov <koct9i@gmail.com> wrote:
> On Thu, Jan 7, 2016 at 3:54 PM, Eric Dumazet <edumazet@google.com> wrote:
want to look at git history to find out why it is done this way.
>>
>> TCP performance is critical for some of us, and doing such trick avoid
>> one cache miss per skb in some critical list traversals.
>
> Right. This way tcp stuff perfectly fits into leftovers of first cache line.
> Then probably it's better to put ipv4/ipv6 cb into second line from
> the beginning.

Then IP forwarding might be slower.

Look, each layer (TCP , IP, ....) can organize its skb->cb[] as it wants.
Nobody tries to 'make universal room' for IPCB, since only IP layer wants it.

TCP could even find a way in the future to no longer hold a copy of
IPCB in the input skb,
if code is reorganized a bit.

Note that skbs for output path in TCP do not need IPCB at all.

Only when skb leaves TCP and enter IP, skb->cb[] content is scratched.

\
 
 \ /
  Last update: 2016-01-07 21:21    [W:0.058 / U:0.444 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site