Hi all,
PyPy's JIT now supports the 64-bit PowerPC architecture! This is the third architecture supported, in addition to x86 (32 and 64) and ARM (32-bit only). More precisely, we support Linux running the big- and the little-endian variants of ppc64. Thanks to IBM for funding this work!
The new JIT backend has been merged into "default". You should be able to translate PPC versions as usual directly on the machines. For the foreseeable future, I will compile and distribute binary versions corresponding to the official releases (for Fedora), but of course I'd welcome it if someone else could step in and do it. Also, it is unclear yet if we will run a buildbot.
To check that the result performs well, I logged in a ppc64le machine and ran the usual benchmark suite of PyPy (minus sqlitesynth: sqlite was not installed on that machine). I ran it twice at a difference of 12 hours, as an attempt to reduce risks caused by other users suddenly using the machine. The machine was overall relatively quiet. Of course, this is scientifically not good enough; it is what I could come up with given the limited resources.
Here are the results, where the numbers are speed-up factors between the non-jit and the jit version of PyPy. The first column is x86-64, for reference. The second and third columns are the two ppc64le runs. All are Linux. A few benchmarks are not reported here because the runner doesn't execute them on non-jit (however, apart from sqlitesynth, they all worked).
ai 13.7342 16.1659 14.9091
bm_chameleon 8.5944 8.5858 8.66
bm_dulwich_log 5.1256 5.4368 5.5928
bm_krakatau 5.5201 2.3915 2.3452
bm_mako 8.4802 6.8937 6.9335
bm_mdp 2.0315 1.7162 1.9131
chaos 56.9705 57.2608 56.2374
sphinx
crypto_pyaes 62.505 80.149 79.7801
deltablue 3.3403 5.1199 4.7872
django 28.9829 23.206 23.47
eparse 2.3164 2.6281 2.589
fannkuch 9.1242 15.1768 11.3906
float 13.8145 17.2582 17.2451
genshi_text 16.4608 13.9398 13.7998
genshi_xml 8.2782 8.0879 9.2315
go 6.7458 11.8226 15.4183
hexiom2 24.3612 34.7991 33.4734
html5lib 5.4515 5.5186 5.365
json_bench 28.8774 29.5022 28.8897
meteor-contest 5.1518 5.6567 5.7514
nbody_modified 20.6138 22.5466 21.3992
pidigits 1.0118 1.022 1.0829
pyflate-fast 9.0684 10.0168 10.3119
pypy_interp 3.3977 3.9307 3.8798
raytrace-simple 69.0114 108.8875 127.1518
richards 94.1863 118.1257 102.1906
rietveld 3.2421 3.0126 3.1592
scimark_fft
scimark_lu
scimark_montecarlo
scimark_sor
scimark_sparsematmul
slowspitfire 2.8539 3.3924 3.5541
spambayes 5.0646 6.3446 6.237
spectral-norm 41.9148 42.1831 43.2913
spitfire 3.8788 4.8214 4.701
spitfire_cstringio 7.606 9.1809 9.1691
sqlitesynth
sympy_expand 2.9537 2.0705 1.9299
sympy_integrate 4.3805 4.3467 4.7052
sympy_str 1.5431 1.6248 1.5825
sympy_sum 6.2519 6.096 5.6643
telco 61.2416 54.7187 55.1705
trans2_annotate
trans2_rtype
trans2_backendopt
trans2_database
trans2_source
twisted_iteration 55.5019 51.5127 63.0592
twisted_names 8.2262 9.0062 10.306
twisted_pb 12.1134 13.644 12.1177
twisted_tcp 4.9778 1.934 5.4931
GEOMETRIC MEAN 9.31 9.70 10.01
The last line reports the geometric mean of each column. We see that the goal was reached: PyPy's JIT actually improves performance by a factor of around 9.7 to 10 times on ppc64le. By comparison, it "only" improves performance by a factor 9.3 on Intel x86-64. I don't know why, but I'd guess it mostly means that a non-jitted PyPy performs slightly better on Intel than it does on PowerPC.
Why is that? Actually, if we do the same comparison with an ARM column too, we also get higher numbers there than on Intel. When we discovered that a few years ago, we guessed that on ARM running the whole interpreter in PyPy takes up a lot of resources, e.g. of instruction cache, which the JIT's assembler doesn't need any more after the process is warmed up. And caches are much bigger on Intel. However, PowerPC is much closer to Intel, so this argument doesn't work for PowerPC. But there are other more subtle variants of it. Notably, Intel is doing crazy things about branch prediction, which likely helps a big interpreter---both the non-JITted PyPy and CPython, and both for the interpreter's main loop itself and for the numerous indirect branches that depend on the types of the objects. Maybe the PowerPC is as good as Intel, and so this argument doesn't work either. Another one would be: on PowerPC I did notice that gcc itself is not perfect at optimization. During development of this backend, I often looked at assembler produced by gcc, and there are a number of small inefficiencies there. All these are factors that slow down the non-JITted version of PyPy, but don't influence the speed of the assembler produced just-in-time.
Anyway, this is just guessing. The fact remains that PyPy can now be used on PowerPC machines. Have fun!
A bientôt,
Armin.
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