On Thu, 15 Dec 2005, Stephen Hemminger wrote:
> On Fri, 16 Dec 2005 03:26:31 +0100
> Andi Kleen <[EMAIL PROTECTED]> wrote:
>
> > On Thu, Dec 15, 2005 at 08:35:32PM -0500, Bill Fink wrote:
> > > On Fri, 16 Dec 2005, Andi Kleen wrote:
> > >
> > > > > It appears that it is getting CPU starved for some reason (note the
> > > > > 43%/40% transmitter CPU usage versus the 99%/99% CPU usage for the
> > > > > 2.6.12.6 case).
> > > >
> > > > What happens when you turn off tso in ethtool?
> > >
> > > Thanks!!! That did the trick.
> >
> > TSO is still a bit of work in progress. The old 2.6.12 TSO code
> > actually ignored the congestion window and was illegal in benchmarks etc
> > (and might have even been dangerous to the internet). That was fixed,
> > but performance still didn't fully recover. It's a tricky problem.
>
> And it wasn't till 2.6.15 that we got the fix in to correctly
> increase cwnd with TSO.
Update:
I just now tested with 2.6.15-rc7 and it seems to work fine with
TSO enabled.
chance% cat /proc/version
Linux version 2.6.15-rc7-bf-smp ([EMAIL PROTECTED]) (gcc version 3.2 20020903
(Red Hat Linux 8.0 3.2-7)) #1 SMP Wed Dec 28 19:35:55 EST 2005
[EMAIL PROTECTED] ethtool -k eth0
Offload parameters for eth0:
rx-checksumming: on
tx-checksumming: on
scatter-gather: on
tcp segmentation offload: on
chance% nuttcp -w2m 192.168.88.8
6054.1250 MB / 10.01 sec = 5073.1546 Mbps 100 %TX 72 %RX
chance% nuttcp -r -w2m 192.168.88.8
6090.4375 MB / 10.01 sec = 5103.6174 Mbps 100 %TX 70 %RX
That's expected TCP performance levels of slightly over 5 Gbps,
although I thought I might get some CPU back with TSO enabled
(note the transmitter is still pegged at 100%).
Would the following patch be at all useful for the 2.6.14.x stable
series, since enabling TSO there causes a 40% or greater TCP performance
penalty, or is 2.6.15 final so imminenent that it wouldn't be
considered useful?
Signed-off-by: Bill Fink <[EMAIL PROTECTED]>
--- linux-2.6.14.3.orig/drivers/net/ixgb/ixgb_main.c 2005-11-24
17:10:21.000000000 -0500
+++ linux-2.6.14.3/drivers/net/ixgb/ixgb_main.c 2005-12-28 01:06:05.000000000
-0500
@@ -445,7 +445,8 @@
NETIF_F_HW_VLAN_RX |
NETIF_F_HW_VLAN_FILTER;
#ifdef NETIF_F_TSO
- netdev->features |= NETIF_F_TSO;
+ /* TSO not performant at present - disable by default */
+ netdev->features &= ~NETIF_F_TSO;
#endif
if(pci_using_dac)
-
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