* user space checksum
@ 2005-05-22 6:51 raz ben jehuda
2005-05-26 19:47 ` Stephen Hemminger
0 siblings, 1 reply; 2+ messages in thread
From: raz ben jehuda @ 2005-05-22 6:51 UTC (permalink / raw)
To: netdev
I do not know if this was ever suggested.so i'll try any way.
Why not give the user the chance to supply the kernel/card with the
checksums instead of having the kernel/network card do the work ?
This is because a user is aware to the data he sends and he can optimize
the data checksum calculations more than anyone else. for instance a web
server sends its html pages, which are static data. it can pre-calculate
the checksums.
Anyone ?
--
Raz
Long Live The Penguin
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: user space checksum
2005-05-22 6:51 user space checksum raz ben jehuda
@ 2005-05-26 19:47 ` Stephen Hemminger
0 siblings, 0 replies; 2+ messages in thread
From: Stephen Hemminger @ 2005-05-26 19:47 UTC (permalink / raw)
To: raz ben jehuda; +Cc: netdev
On Sun, 22 May 2005 09:51:48 +0300
raz ben jehuda <razb@bitband.com> wrote:
> I do not know if this was ever suggested.so i'll try any way.
> Why not give the user the chance to supply the kernel/card with the
> checksums instead of having the kernel/network card do the work ?
A bad idea for two reasons:
* application data units (APDU) do not match transport data units
for a stream oriented protocol.
* computing checksum is done for almost nothing as part
of the copy from user to kernel space. Modern CPU cache's
make computation cost << memory access cost.
> This is because a user is aware to the data he sends and he can optimize
> the data checksum calculations more than anyone else. for instance a web
> server sends its html pages, which are static data. it can pre-calculate
> the checksums.
Tcp will compute different transfer size's based on the congestion
window of the connection, and header part will be different.
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