Optimizing Lua Applications for LuaJIT and OpenResty - - PowerPoint PPT Presentation

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Optimizing Lua Applications for LuaJIT and OpenResty - - PowerPoint PPT Presentation

Jan 31, 2023 489 likes •1.35k views

Optimizing Lua Applications for LuaJIT and OpenResty agentzh@openresty.org Yichun Zhang (@agentzh) 2016.9 NGINX + LuaJIT Flame Graphs I/O Off -CPU Flame Graphs # assuming the nginx worker process to be analyzed is 10901.

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Optimizing Lua Applications for LuaJIT and OpenResty ☺agentzh@openresty.org☺

Yichun Zhang (@agentzh)

2016.9
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♡ NGINX + LuaJIT

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☺ Flame Graphs

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☺ I/O

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♡ Off-CPU Flame Graphs

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SLIDE 14 # assuming the nginx worker process to be analyzed is 10901. ./sample­bt­off­cpu ­p 10901 ­t 5 > a.bt
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# using Brendan Gregg's flame graph tools: $ stackcollapse­stap.pl a.bt > a.cbt $ flamegraph.pl a.cbt > a.svg

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♡ Synchronously nonblocking I/O

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♡ Light threads & semaphores

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local thread_A, err = ngx.thread.spawn(func1) ­­ thread_A keeps running asynchronously ­­ in the background of the current ­­ "light thread".

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local ok, res1, res2 = ngx.thread.wait(thread_A, thread_B)

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local ok, err = ngx.thread.kill(thread_A)

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♡ Full-Duplex Cosockets

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local sock = ngx.socket.tcp() local ok, err = sock:connect("www.cloudflare.com", 443)

  • k, err = sock:sslhandshake(

false, ­­ disable SSL session "www.cloudflare.com", ­­ SNI name true ­­ verify everything )

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♡ Timers and Sleeps

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­­ create a timer triggered after 1 sec ngx.timer.at(1000, function (premature) do_something() end) ­­ sleeps for 1 sec then continue ngx.sleep(1000)

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☺ CPU

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♡ on-CPU Flame Graphs

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♡ Lua-land Flame Graphs

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http://agentzh.org/misc/flamegraph/lua-on-cpu-local-waf-jitted-only.svg

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lj­lua­stacks.sxx ­­arg time=5 \ ­­skip­badvars \ ­x 6949 \ > a.bt

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♡ LuaJIT Built-in Profiler vs SystemTap Sampling

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♡ Dynamic Allocations & Garbage Collection

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Lua tables

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lj_tab_new lj_tab_resize lj_tab_len

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table.new(10, 20)

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table.clear(tb)

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tb[key1] = val1 tb[key1] = nil tb[key2] = val2

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Lua strings

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? s = s .. r

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­­ tb[#tb + 1] is slow! idx = idx + 1 tb[idx] = r s = table.concat(tb)

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? string.sub(s, i, i)

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string.byte(s, i, i)

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Lua functions

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foo = function (...) ... end

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♡ JITting vs Interpreting

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lua-resty-core

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jit.v jit.dump

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lj­lua­stacks.sxx ­­arg nojit=1 ... lj­lua­stacks.sxx ­­arg nointerp=1 ...

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♡ Biased vs Unbiased Branching

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♡ Lua code generation atop LuaJIT JIT over a JIT!

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♡ Regexes

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/ \d+ \. \d+ | \. \d+ | \d+ /x

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sregex

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☺ Memory

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♡ Memory-Leak Flame Graphs

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♡ GC Object Analaysis

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SLIDE 74 $ lj­gc­objs.sxx ­x 14378 ­D MAXACTION=200000 Start tracing 14378 (/opt/nginx/sbin/nginx) main machine code area size: 65536 bytes C callback machine code size: 4096 bytes GC total size: 9683407 bytes GC state: pause 27948 table objects: max=131112, avg=106, min=32, sum=2983944 (in bytes) 22343 string objects: max=1421562, avg=198, min=18, sum=4432482 (in bytes) 12168 userdata objects: max=8916, avg=50, min=27, sum=619223 (in bytes) 2837 function objects: max=148, avg=27, min=20, sum=78264 (in bytes) 1200 upvalue objects: max=24, avg=24, min=24, sum=28800 (in bytes) 650 proto objects: max=3860, avg=313, min=74, sum=203902 (in bytes) 349 thread objects: max=1648, avg=774, min=424, sum=270464 (in bytes) 202 trace objects: max=1560, avg=375, min=160, sum=75832 (in bytes) 9 cdata objects: max=36, avg=17, min=12, sum=156 (in bytes) JIT state size: 7696 bytes global state tmpbuf size: 710772 bytes C type state size: 4568 bytes My GC walker detected for total 9683407 bytes. 45008 microseconds elapsed in the probe handler.
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SLIDE 75 (gdb) lgcstat 15172 str objects: max=2956, avg = 51, min=18, sum=779126 987 upval objects: max=24, avg = 24, min=24, sum=23688 104 thread objects: max=1648, avg = 1622, min=528, sum=168784 431 proto objects: max=226274, avg = 2234, min=78, sum=963196 952 func objects: max=144, avg = 30, min=20, sum=28900 446 trace objects: max=23400, avg = 1857, min=160, sum=828604 2965 cdata objects: max=4112, avg = 17, min=12, sum=51576 18961 tab objects: max=24608, avg = 207, min=32, sum=3943256 9 udata objects: max=176095, avg = 39313, min=32, sum=353822
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♡ Streaming Processing

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♡ Streaming Regex (sregex)

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♡ The cost of abstractions

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♡ The oppportunities of new abstractions

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♡ Business-Level Domain Specific Languages

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ModSecurity's syntax sucks.

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☺ Any questions? ☺

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