Messages in this thread | | | Date | Thu, 11 Nov 2004 16:00:21 -0800 | From | "David S. Miller" <> | Subject | Re: [Bonding-devel][PATCH]Zero Copy Transmit Support (Update) |
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On Fri, 12 Nov 2004 15:51:49 -0800 (PST) Radheka Godse <radheka.godse@intel.com> wrote:
> - > + > + /* We let the bond device publish all hardware > + * acceleration features possible. This is OK, > + * since if an skb is passed from the bond to > + * a slave that doesn't support one of those > + * features, everything is fixed in the > + * dev_queue_xmit() function (e.g. calculate > + * check sum, linearize the skb, etc.). > + */
This is very inefficient if the bond slaves don't support these features.
I believe you when you say you saw improvement in the case where the slaves do support TSO, but if you test a non-TSO slave case I bet you'll see a marked decrease in system utilization at least.
The upper layers need to know the precise capabilities of the device in order to optimize the copy from userspace, the checksumming, and the data gathering into the SKB.
Therefore, if you "fake it out" like this without checking what the slaves actually support, then a lot of wasted cpu time will be spent in each dev_queue_xmit() path. There will in many cases be multiple passes over the data instead of one, and it is possible to introduce an extra data copy as well.
I would recommend instead the following algorithm. Publish only the capabilities which all slaves support. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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