On 26/03/13 10:52, James Harper wrote:

quoted

quoted

It's not clear why 19 or 20 were suggested as possible values.
I checked back to 2.6.18 and MAX_SKB_FRAGS there is
(65536/PAGE_SIZE + 2)

Because the check is >= MAX_SKB_FRAGS originally and James Harper
told me that "Windows stops counting on 20".

I've obviously not been clear enough here... GPLPV stopped counting
at 20 (only needed to know if <20 or not). Windows itself can submit
a packet to NDIS with hundreds of buffers. It doesn't really matter
if it's 21 or 1021, I just didn't want to be misquoted.

This still isn't clear.  What's the maximum number of ring entries that
GPLPV driver will use per packet?  Are you saying it's 20?  If so how
has the GPLPV driver ever worked well with Linux's netback (with its
historical limit of 18)?

David