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Date: Thu, 20 Jun 2013 18:47:53 +0400
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To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: PHP Internals <internals@lists.php.net>, Rasmus Lerdorf <rasmus@lerdorf.com>, pollita@php.net
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Subject: Re: [PHP-DEV] ARM performance and GOTO executor
From: dmitry@zend.com (Dmitry Stogov)

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GOTO-executor is faster on x86 as well.
It may be proven by synthetic benchmarks, however. on real-life
applications it doesn't make any significant difference (sometimes it even
slowdown).

I'm not sure how we should generate (and test) zend_vm_execute-goto.h.
Probably the only good option is generating all the different executors at
once and may be even linking them all together to select one at run-time.

FREE_OP2() in BRK/CONT my be removed.

Thanks. Dmitry.


On Thu, Jun 20, 2013 at 5:55 PM, Ard Biesheuvel
<ard.biesheuvel@linaro.org>wrote:

> Hello all,
>
> I am working on ARM server performance tuning, and I have been playing
> around a bit with the various executor modes and zend_vm_gen.php.
>
> As it turns out (scroll down for numbers), the GOTO executor is much
> faster than the default CALL executor on ARM, partly due to fewer branch
> mispredictions (as perf tells me) but there are probably other factors at
> play here as well.
>
> My question to you is if we could parametrize this in the build system,
> for instance by adding alternate files zend_vm_opcodes-goto.h and
> zend_vm_execute-goto.h to the tree, and selecting those when targeting ARM
> (and perhaps other archs that may prefer GOTO over CALL as well). Or is
> there a better way of including/selecting alternate executors?
>
> Also, when playing around, I noticed that building the executor without
> specialization is broken, as there are erroneous FREE_OP2() calls left
> behind in the handlers for 'break' and 'continue'. If nobody objects, I
> will remove them (zend_vm_def.h lines 3302 and 3314)
>
> Regards,
> Ard.
>
>
> ARM Cortex-A15 @ 1.7 GHz with default executor (specialized CALL)
> ==============================**==============================**=====
>
> simple             0.358
> simplecall         0.396
> simpleucall        0.419
> simpleudcall       0.458
> mandel             0.839
> mandel2            1.038
> ackermann(7)       0.400
> ary(50000)         0.096
> ary2(50000)        0.087
> ary3(2000)         0.490
> fibo(30)           1.157
> hash1(50000)       0.135
> hash2(500)         0.096
> heapsort(20000)    0.266
> matrix(20)         0.309
> nestedloop(12)     0.499
> sieve(30)          0.363
> strcat(200000)     0.046
> ------------------------
> Total              7.449
>
>  Performance counter stats for 'php Zend/bench.php':
>
>        7444.535230 task-clock        #    0.983 CPUs utilized
>                103 context-switches  #    0.014 K/sec
>                  9 cpu-migrations    #    0.001 K/sec
>               5963 page-faults       #    0.801 K/sec
>        12728701964 cycles            #    1.710 GHz
>        13603248229 instructions      #    1.07  insns per cycle
>         2633774500 branches          #  353.786 M/sec
>          118799433 branch-misses     #    4.51% of all branches
>
>        7.570311211 seconds time elapsed
>
>
> ARM Cortex-A15 @ 1.7 GHz with specialized GOTO executor
> ==============================**=========================
>
> simple             0.185
> simplecall         0.295
> simpleucall        0.249
> simpleudcall       0.257
> mandel             0.349
> mandel2            0.529
> ackermann(7)       0.252
> ary(50000)         0.061
> ary2(50000)        0.060
> ary3(2000)         0.393
> fibo(30)           0.798
> hash1(50000)       0.092
> hash2(500)         0.079
> heapsort(20000)    0.195
> matrix(20)         0.206
> nestedloop(12)     0.214
> sieve(30)          0.241
> strcat(200000)     0.025
> ------------------------
> Total              4.479
>
>  Performance counter stats for '~/php Zend/bench.php':
>
>        4468.040559 task-clock        #    0.983 CPUs utilized
>                 79 context-switches  #    0.018 K/sec
>                  9 cpu-migrations    #    0.002 K/sec
>               5062 page-faults       #    0.001 M/sec
>         7561345552 cycles            #    1.692 GHz
>        11297962039 instructions      #    1.49  insns per cycle
>         2121936756 branches          #  474.914 M/sec
>           22190686 branch-misses     #    1.05% of all branches
>
>        4.545350085 seconds time elapsed
>
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