Messages in this thread | | | Date | Tue, 24 Aug 2010 13:49:14 -0600 (Mountain Daylight Time) | From | Marc Aurele La France <> | Subject | Re: RFC: MTU for serving NFS on Infiniband |
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On Tue, 24 Aug 2010, Ben Hutchings wrote: > On Tue, 2010-08-24 at 09:14 -0600, Marc Aurele La France wrote: >> On Mon, 23 Aug 2010, Stephen Hemminger wrote: >>> On Mon, 23 Aug 2010 08:44:37 -0600 (MDT) >>> Marc Aurele La France <tsi@ualberta.ca> wrote: >>>> In regrouping for my next tack at this, I noticed that all stack traces go >>>> through ip_append_data(). This would be ipv6_append_data() in the IPv6 case. >>>> A _very_ rough draft that would have ip_append_data() temporarily drop down >>>> to a smaller fake MTU follows ...
>>> Why doesn't NFS generate page size fragments? Does Infiniband or your >>> device not support this? Any thing that requires higher order allocation >>> is going to unstable under load. Let's fix the cause not the apply bandaid >>> solution to the symptom.
>> From what I can tell, IP fragmentation is done centrally. > [...]
> Stephen and I are not talking about IP fragmentation, but about the > ability to append 'fragments' to an skb rather than putting the entire > packet payload in a linear buffer. See > <http://vger.kernel.org/~davem/skb_data.html>.
Any payload has to either fit in the MTU, or has to be broken up into MTU-sized (or less) fragments, come hell or high water. That this is done centrally is a good thing. It is the "(or less)" part that I am working towards here.
Marc.
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