The document details Ruby performance profiling techniques presented by Alexey Tulia, emphasizing the impact of garbage collection on Ruby applications and providing guidance on optimizing performance through various methods, including C extensions and profiling tools. It highlights the importance of understanding string performance and offers commands for tracing system calls. Additionally, it stresses the importance of not prematurely optimizing code and offers principles for effective profiling.

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?