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From: Adrian Chadd <adrian@freebsd.org>
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Cc: freebsd-arm@freebsd.org, freebsd-mips@freebsd.org
Subject: Re: busdma buffer management enhancements - call for review and test
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Hiya,

This is pretty neat work. :)

But by converting drivers to use individual uma allocations, aren't
you risking fragmenting FIFO rings and such? I'm sure there are
platforms out there whose memory controllers operate on minimum sized
bits (say, 512 byte chunks for some intel PC chipsets, if I'm not
mistaken) .. right now ath(4)'s RX descriptors are almost always kept
in order of allocation, but with your proposal it's quite possible
they'll be spread all around the the (fixed size) UMA slab.

I can't help but think there's some larger scale issues here that are
slightly orthogonal to the requirements of (small) embedded platforms.



Adrian