Ceph Jerasure and ISA plugins benchmarks

In Ceph, a pool can be configured to use erasure coding instead of replication to save space. When used with Intel processors, the default Jerasure plugin that computes erasure code can be replaced by the ISA plugin for better write performances. Here is how they compare on a Intel(R) Xeon(R) CPU E3-1245 V2 @ 3.40GHz.

Encoding and decoding all used 4KB objects which is the default stripe width. Two variants of the jerasure plugins were used: Generic (jerasure_generic) and SIMD (erasure_sse4) which is used when running on an Intel processor with SIMD instructions.
This benchmark was run after compiling from sources using

$ ( cd src ; make ceph_erasure_code_benchmark )
$ TOTAL_SIZE=$((4 * 1024 * 1024 * 1024)) \
CEPH_ERASURE_CODE_BENCHMARK=src/ceph_erasure_code_benchmark \
  qa/workunits/erasure-code/bench.sh fplot | \
  tee qa/workunits/erasure-code/bench.js

and displayed with

firefox qa/workunits/erasure-code/bench.html

Improving Ceph python scripts tests

The Ceph command line and ceph-disk helper are python scripts for which there are integration tests (ceph-disk.sh and test.sh). It would be useful to add unit tests and pep8 checks.
It can be done by creating a python module instead of an isolated file (see for instance ceph-detect-init) with a tox.ini file including pep8, python2 and python3 test environments.
Since Ceph relies on autotools, the setup.py can be used with -local targets. For instance:

        python setup.py build
	python setup.py clean
	python setup.py install --root=$(DESTDIR) --install-layout=deb

Note the double : meaning it appends to an existing rule instead of overriding it. The –root=$(DESTDIR) will install the module files in the appropriate directory when building packages.
tox uses pip to fetch dependencies required to run tests from PyPI, but tests sometime run without network access. The depedencies can be collected by wheel with something like:

pip wheel -r requirements.txt

It will create a wheelhouse directory which can later be used with

pip install --no-index --use-wheel --find-links=wheelhouse \
  -r requirements.txt

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