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Date: Fri, 3 May 2019 15:37:11 -0400
From: Garrett Wollman <wollman@csail.mit.edu>
To: Konstantin Belousov <kostikbel@gmail.com>
Cc: freebsd-net@freebsd.org
Subject: Re: Disabling 9k jumbo clusters on mce(4)
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<<On Fri, 3 May 2019 20:47:15 +0300, Konstantin Belousov <kostikbel@gmail.com> said:

> On Fri, May 03, 2019 at 12:55:54PM -0400, Garrett Wollman wrote:
>> Does anyone have an easy patch to keep mce(4) from trying to use 9k
>> jumbo mbuf clusters?  I think I went down this road once before but
>> the fix wasn't as obvious as it is for the Intel drivers.  (I assume
>> the hardware is not so broken that it requires packets to be stored in
>> contiguous physical memory.)
> mce(4) only uses 9k clusters when you configured jumbo size larger than 4k.
> See r336407.

Yes, and the point is to make it not use them *ever*, no matter what
the MTU is.  9k clusters are Bad News; given the choice I would just
as soon rip out all the code for greater-than-page-size clusters, but
that would be way more divergence-from-upstream in my source tree than
I can reasonably manage.

-GAWollman