Лекция посвящена профилированию Ruby-кода, анализу результатов работы профилировщика и использованию этих данных для оптимизации производительности.

1. Ruby performance
profiling
Minsk, SaM Solutions, 2013
Presented by Alexey Tulia
@AlexeyTulia, github.com/crible

2. Ruby. A programmer’s best friend

3. Ruby implementations

5. Reasons?

6. Garbage collection
Slow methods call

7. one iteration takes ~ 100ms
Garbage collection
Need one Gb?
Expect 128 GC calls!
You lose 128*0,1 = 12,8 sec
Allocated memory never returns to the system!
runs on every 8Mb of allocated memory

8. Garbage collection
More objects allocation -> more GC calls -> slow code

9. RUBY_HEAP_MIN_SLOTS=8000000
RUBY_GC_MALLOC_LIMIT=10000
Garbage collection tuning
performance patches

10. Ruby String performance
require 'benchmark'
ITERATIONS = 1000000
def run(str, bench)
bench.report("#{str.length + 1} chars") do
ITERATIONS.times do
new_string = str + 'x'
end
end
end
Benchmark.bm do |bench|
run("12345678901234567890", bench)
run("123456789012345678901", bench)
run("1234567890123456789012", bench)
run("12345678901234567890123", bench)
run("123456789012345678901234", bench)
run("1234567890123456789012345", bench)
run("12345678901234567890123456", bench)
end
user system total real
21 chars 0.250000 0.000000 0.250000 ( 0.247459)
22 chars 0.250000 0.000000 0.250000 ( 0.246954)
23 chars 0.250000 0.000000 0.250000 ( 0.248440)
24 chars 0.480000 0.000000 0.480000 ( 0.478391)
25 chars 0.480000 0.000000 0.480000 ( 0.479662)
26 chars 0.480000 0.000000 0.480000 ( 0.481211)
27 chars 0.490000 0.000000 0.490000 ( 0.490404)

11. Ruby String performance
Heap strings
Shared strings
Embedded strings

12. struct RString {
long len;
char *ptr;
};
Ruby String performance
struct RString {
long len;
char *ptr;
VALUE shared;
};
struct RString {
char ary[RSTRING_EMBED_LEN_MAX +1];
}
RSTRING_EMBED_LEN_MAX = 23

13. Slow methods call

14. What can I do to improve performance?
Use C extensions or gems
Use plain SQL instead of frameworks
Use CPU and memory profiling
Use Rubinius or JRuby

18. STRACE
trace system calls and signals
strace -cp <pid>
strace -ttTp <pid> -o <file>

19. % time seconds uses/call calls errors syscall
50,39 0,00064 0 1197 592 read
34,56 0,00044 0 609 writev
14,96 0,000019 0 1226 epoll_ctl
0,00 0,000000 0 4 close
0,00 0,000000 0 1 select
0,00 0,000000 0 4 socket
0,00 0,000000 0 4 4 connect
0,00 0,000000 0 1057 epoll_wait
100,0 0,000127 4134 596 total
strace -cp <pid>

20. LTRACE
trace dynamic library calls
ltrace -F <conf_file> -bg -x <symbol> -p pid

21. ltrace -F <conf_file> -bg -x <symbol> -p pid
-F <conf_file>
int mysql_real_query(addr,string,ulong);
void garbage_collect(void);
int memcached_set(addr,string,ulong,string,ulong);

22. ltrace -x garbage_collect
ltrace -x mysql_real_query
mysql_real_query(0x1c9e0500, "SET NAMES 'UTF8'", 16) = 0 <0.000324>
mysql_real_query(0x1c9e0500, "SET SQL_AUTO_IS_NULL=0", 22) = 0 <0.000322>
mysql_real_query(0x19c7a500, "SELECT * FROM `users`", 21) = 0 <1.206506>
mysql_real_query(0x1c9e0500, "COMMIT", 6) = 0 <0.000181>

23. RUBY-PROF
fast code profiler for Ruby

24. %self total self child calls name
------------------------------------------------------------------------
8.39 0.54 0.23 0.31 602 Array#each_index
7.30 0.41 0.20 0.21 1227 Integer#gcd
6.20 0.49 0.17 0.32 5760 Timecell#date
5.11 0.15 0.14 0.01 1 Magick::Image#to_blob
RUBY-PROF

25. KCachegrind
a tool for visualisation
http://kcachegrind.sourceforge.net

26. KCachegrind

27. KCachegrind

29. PERFTOOLS.RB
google’s performance tools for ruby code
CPUPROFILE=/tmp/myprof
pprof --calgrind ./myapp /tmp/myprof
gem install perftools.rb
RUBYOPT="-r`gem which perftools | tail -1`"
ruby my_app.rb

30. PERFTOOLS.RB
CPUPROFILE_REALTIME = 1
CPU/wall time
CPUPROFILE_OBJECTS = 1
CPUPROFILE_METHODS = 1

31. When should I stop performance optimisation?
Premature optimization is the root of all evil
(c) Donald Knuth

32. Make it work
Make it right
Make it fast

33. What should I remeber before profiling?
Turn GC off (GC.disable)
class Foo
def do_smth
return "x" * 1024 # take one Kb of memory
end
end
smth = "x" * 7999999 # alloc almost 8Mb
Foo.new.do_smth # here GC will be called
do_smth is so slow!!!

36. Questions?