Large pages, large blocks, and large problems [LWN.net]

Large pages, large blocks, and large problems

Posted Sep 20, 2007 1:58 UTC (Thu) by sayler (guest, #3164)
In reply to: Large pages, large blocks, and large problems by drag
Parent article: Large pages, large blocks, and large problems

In general, I agree with what you say, but keep in mind that Ethernet frames are inherently variable in size, that is, you can have 1500, 1501, 1502, ... byte frames and the transmission time will increase nearly linearly.

We have much coarser choices for page sizes. Even on Alpha (which apparently did a good job here), page size choices were something like 8k ** 2*N where N ran between 0 and 3..

There is some other somewhat interesting data here: http://lists.freebsd.org/pipermail/freebsd-hackers/2003-O... showing measured {i,d}tlb size for various page sizes on various uArchs.

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Large pages, large blocks, and large problems

Posted Sep 21, 2007 15:16 UTC (Fri) by jamesh (guest, #1159) [Link]

It is true that ethernet frames are variable size, but it also states that the maximum payload size is 1500 bytes as the grandparent post says. You need to have some upper limit in order to make hardware that can reliably store and forward packets (as a switch would need to do when forwarding a packet to a slower network).

Ethernet frames larger than 1500 bytes are non-standard and commonly known as "jumbo frames". And as you can guess, they'll only work if all the hardware involved in the link supports the larger frames.