[erlang-questions] io_lib:format R16B03 performance and jsx impact

[Dmitry Kolesnikov]

Hello,

Here I’ve compiled a small project to benchmark the issue:

git clone https://github.com/fogfish/fjsx
make
make run
(fjsx@REDACTED)1> fjsx:run().

My results are following:
R15B03: min 2.9K, avg 3.1K, max 3.3K
R16B03: min 2.7K, avg 2.8K, max 3.0K 

(In production I do much more staff, it shown even worse degradation)

I run the test on virtual machine, cent os 6 x86_64 with 4 virtual CPU (underlying HW MacBook Pro i5, 2.5GHz).
Virtual CPU
vendor_id	: GenuineIntel
cpu family	: 6
model		: 58
model name	: Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
stepping	: 9
cpu MHz		: 2535.252
cache size	: 6144 KB
physical id	: 0
siblings	: 4
core id		: 3
cpu cores	: 4
apicid		: 3
initial apicid	: 3
fpu		: yes
fpu_exception	: yes
cpuid level	: 5
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx rdtscp lm constant_tsc rep_good pni ssse3 lahf_lm
bogomips	: 5070.50
clflush size	: 64
cache_alignment	: 64
address sizes	: 36 bits physical, 48 bits virtual
power management:

otp configuration is identical for R15 and R16

R15B03: config.log
  $ ./configure --prefix=/usr/local/otp_R15B03 --enable-threads --enable-smp-support --enable-kernel-poll --enable-hipe --disable-dynamic-ssl-lib --with-ssl=/usr/local/ssl --enable-native-libs

R16B03: config.log
  $ ./configure --prefix=/usr/local/otp_R16B03 --enable-threads --enable-smp-support --enable-kernel-poll --enable-hipe --disable-dynamic-ssl-lib --with-ssl=/usr/local/ssl --enable-native-libs

I have not run the test on real HW:
 - my mac’s OTP configurations are different R16B03 enables --enable-darwin-64bit therefor it outperforms R15
 - my production is virtual machines 

I’ve been using eep to profile the issue. You can go same to compare R16 and R15 differences.

Best Regards, 
Dmitry

On 28 Jan 2014, at 11:54, Lukas Larsson <lukas@REDACTED> wrote:

> Hello,
> 
> The code for formatting float when doing it through io_lib:format it written in pure Erlang. The reason that io_lib:format is implemented in Erlang is because it allows much greater cross platform formatting capabilities, alas at the cost of performance. 
> 
> Why you see a performance drop in between R15B03 to R16B03 I don't know, if you could create a minimal reproducible benchmark that shows the difference that would be great.
> 
> If you want to have a speedy conversion of something you know is a float to a textual format you should use float_to_list/binary as that is meant to be a fast conversion, but with less flexibility.
> 
> Lukas
> 
> 
> On Tue, Jan 28, 2014 at 10:05 AM, Max Lapshin <max.lapshin@REDACTED> wrote:
> btw, why io_lib:format is so slow? simple changing it to nif with fprintf reduces cpu a lot.
> 
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> 

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