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On 06/07/15 18:23, James Page wrote:
>> The ceph Debian package git repository only contains very little
>>> reasoning about the change. James can you please expand on this
>>> a bit? In general I would prefer to have changes like this in
>>> their own commit and not mixed with unrelated changelog
>>> updates. Did the Hammer release not build with the jerasure in
>>> Debian or are you just afraid of unexpected results if the
>>> Debian package is built with another version of jerasure than
>>> what they ship in their source code? These would IMO be valid
>>> reasons to (temporarily) remove the patch.
> Re-basing the patch - which was turning out to be non-trivial -
> pushed me over the time I had todo this update; as the upload was
> to experimental only, I intended to revisit when time permitted.

I dug into this in a bit more detail today; the Ceph package builds a
number of difference loadable erasure coding plugins, enabling
different cpu feature sets (generic, neon, sse3, sse4); each time
Jerasure and gf-complete are statically linked into the module, built
with the required flags to enable the right CPU instruction codes
(build time, not runtime enablement).

Unless I'm reading the packaging wrong, the jerasure and gf-complete
packages current disable any CPU specific extensions in order to have
a completely generic library that works on any CPU.  So using the
system libraries effectively cripples any CPU optimization that might
be achievable at runtime in Ceph.


- -- 
James Page
Ubuntu and Debian Developer
james.p...@ubuntu.com
jamesp...@debian.org
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