Messages in this thread | | | Date | Thu, 14 Aug 2008 22:30:11 +0400 | From | Vladislav Bolkhovitin <> | Subject | Re: [RFC][PATCH 1/1] cxgb3i: cxgb3 iSCSI initiator |
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Vladislav Bolkhovitin wrote: > David Miller wrote: >> From: Vladislav Bolkhovitin <vst@vlnb.net> >> Date: Wed, 13 Aug 2008 22:35:34 +0400 >> >>> This is because the target sends data in a zero-copy manner, so its >>> CPU is capable to deal with the load, but on the initiator there are >>> additional data copies from skb's to page cache and from page cache >>> to application. >> If you've actually been reading at all what I've been saying in this >> thread you'll see that I've described a method to do this copy >> avoidance in a completely stateless manner. >> >> You don't need to implement a TCP stack in the card in order to do >> data placement optimizations. They can be done completely stateless. > > Sure, I read what you wrote before writing (although, frankly, didn't > get the idea). But I don't think that overall it would be as efficient > as full hardware offload. See my reply to Jeff Garzik about that. > >> Also, large portions of the cpu overhead are transactional costs, >> which are significantly reduced by existing technologies such as >> LRO. > > The test used Myricom Myri-10G cards (myri10ge driver), which support > LRO. And from ethtool -S output I conclude it was enabled. Just in case, > I attached it, so you can recheck me.
Also, there wasn't big difference between MTU 1500 and 9000, which is another point to think that LRO was working.
> Thus, apparently, LRO doesn't make a fundamental difference. Maybe this > particular implementation isn't too efficient, I don't know. I don't > have enough information for that. > > Vlad > >
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