pprof
golang pprof是golang的可视化和性能分析的工具。其提供了可视化的web页面，火焰图等更直观的工具。
可以使用 go tool pprof 进行使用
$ go tool pprof
usage:
Produce output in the specified format.
pprof <format> [options] [binary] <source> ...
Omit the format to get an interactive shell whose commands can be used
to generate various views of a profile
pprof [options] [binary] <source> ...
Omit the format and provide the "-http" flag to get an interactive web
interface at the specified host:port that can be used to navigate through
various views of a profile.
pprof -http [host]:[port] [options] [binary] <source> ...
Details:
Output formats (select at most one):
-callgrind Outputs a graph in callgrind format
-comments Output all profile comments
-disasm Output assembly listings annotated with samples
-dot Outputs a graph in DOT format
-eog Visualize graph through eog
-evince Visualize graph through evince
-gif Outputs a graph image in GIF format
-gv Visualize graph through gv
-kcachegrind Visualize report in KCachegrind
-list Output annotated source for functions matching regexp
-pdf Outputs a graph in PDF format
-peek Output callers/callees of functions matching regexp
-png Outputs a graph image in PNG format
-proto Outputs the profile in compressed protobuf format
-ps Outputs a graph in PS format
-raw Outputs a text representation of the raw profile
-svg Outputs a graph in SVG format
-tags Outputs all tags in the profile
-text Outputs top entries in text form
-top Outputs top entries in text form
-topproto Outputs top entries in compressed protobuf format
-traces Outputs all profile samples in text form
-tree Outputs a text rendering of call graph
-web Visualize graph through web browser
-weblist Display annotated source in a web browser
Options:
-call_tree Create a context-sensitive call tree
-compact_labels Show minimal headers
-divide_by Ratio to divide all samples before visualization
-drop_negative Ignore negative differences
-edgefraction Hide edges below <f>*total
-focus Restricts to samples going through a node matching regexp
-hide Skips nodes matching regexp
-ignore Skips paths going through any nodes matching regexp
-mean Average sample value over first value (count)
-nodecount Max number of nodes to show
-nodefraction Hide nodes below <f>*total
-noinlines Ignore inlines.
-normalize Scales profile based on the base profile.
-output Output filename for file-based outputs
-prune_from Drops any functions below the matched frame.
-relative_percentages Show percentages relative to focused subgraph
-sample_index Sample value to report (0-based index or name)
-show Only show nodes matching regexp
-show_from Drops functions above the highest matched frame.
-source_path Search path for source files
-tagfocus Restricts to samples with tags in range or matched by regexp
-taghide Skip tags matching this regexp
-tagignore Discard samples with tags in range or matched by regexp
-tagshow Only consider tags matching this regexp
-trim Honor nodefraction/edgefraction/nodecount defaults
-trim_path Path to trim from source paths before search
-unit Measurement units to display
Option groups (only set one per group):
cumulative
-cum Sort entries based on cumulative weight
-flat Sort entries based on own weight
granularity
-addresses Aggregate at the address level.
-filefunctions Aggregate at the function level.
-files Aggregate at the file level.
-functions Aggregate at the function level.
-lines Aggregate at the source code line level.
Source options:
-seconds Duration for time-based profile collection
-timeout Timeout in seconds for profile collection
-buildid Override build id for main binary
-add_comment Free-form annotation to add to the profile
Displayed on some reports or with pprof -comments
-diff_base source Source of base profile for comparison
-base source Source of base profile for profile subtraction
profile.pb.gz Profile in compressed protobuf format
legacy_profile Profile in legacy pprof format
http://host/profile URL for profile handler to retrieve
-symbolize= Controls source of symbol information
none Do not attempt symbolization
local Examine only local binaries
fastlocal Only get function names from local binaries
remote Do not examine local binaries
force Force re-symbolization
Binary Local path or build id of binary for symbolization
-tls_cert TLS client certificate file for fetching profile and symbols
-tls_key TLS private key file for fetching profile and symbols
-tls_ca TLS CA certs file for fetching profile and symbols
Misc options:
-http Provide web interface at host:port.
Host is optional and 'localhost' by default.
Port is optional and a randomly available port by default.
-no_browser Skip opening a browser for the interactive web UI.
-tools Search path for object tools
Legacy convenience options:
-inuse_space Same as -sample_index=inuse_space
-inuse_objects Same as -sample_index=inuse_objects
-alloc_space Same as -sample_index=alloc_space
-alloc_objects Same as -sample_index=alloc_objects
-total_delay Same as -sample_index=delay
-contentions Same as -sample_index=contentions
-mean_delay Same as -mean -sample_index=delay
Environment Variables:
PPROF_TMPDIR Location for saved profiles (default $HOME/pprof)
PPROF_TOOLS Search path for object-level tools
PPROF_BINARY_PATH Search path for local binary files
default: $HOME/pprof/binaries
searches $name, $path, $buildid/$name, $path/$buildid
* On Windows, %USERPROFILE% is used instead of $HOME
no profile source specified
安装pprof
go tool pprof 来源于 google/pprof 项目，可以以如下方式安装。
go get -u github.com/google/pprof
安装Graphviz
如果使用 -http 选项指定需要web交互页面，则需要安装 dot 。
Failed to execute dot. Is Graphviz installed?
exec: "dot": executable file not found in $PATH
ubuntu 上通过以下方式安装：
sudo apt install graphviz
启用功能
需要我们的程序开放了pprof web端点。一般建议的方式为,在需要使用的地方引用net/http/pprof包。
import _ "net/http/pprof"
该方式会在默认的 http.DefaultServeMux 中插入debug pprof端点。
// pprof.go:79
func init() {
http.HandleFunc("/debug/pprof/", Index)
http.HandleFunc("/debug/pprof/cmdline", Cmdline)
http.HandleFunc("/debug/pprof/profile", Profile)
http.HandleFunc("/debug/pprof/symbol", Symbol)
http.HandleFunc("/debug/pprof/trace", Trace)
}
不过在一般的开发中不使用该方式，而是使用自定义的handler，如下。
m := http.NewServeMux()
m.Handle("/debug/vars", expvar.Handler()) //用于查看exvar包中的存储的数据，由于一般无人使用该包，所以意义不大。
m.HandleFunc("/debug/pprof/", pprof.Index))
m.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
m.HandleFunc("/debug/pprof/profile", pprof.Profile)
m.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
m.HandleFunc("/debug/pprof/trace", pprof.Trace)
pprof包内调用runtime包中函数以获取各种运行时信息，其包含如下分析指标。
allocs: 过去所有内存分配的样本
block: 导致同步原语阻塞的堆栈跟踪
cmdline: 当前程序的命令行调用，与/proc/中的 cmdline相同
goroutine: 当前所有goroutine的堆栈跟踪
heap: A活动对象的内存分配的采样。您可以指定gc GET参数以在获取堆样本之前运行GC。
mutex: 竞争互斥体持有人的堆栈痕迹
profile: CPU配置文件。您可以在秒GET参数中指定持续时间。获取概要文件后，使用go tool pprof命令调查概要文件。
threadcreate: 导致创建新OS线程的堆栈跟踪
trace: 当前程序执行的痕迹。您可以在秒GET参数中指定持续时间。获取跟踪文件后，请使用go工具trace命令调查跟踪。
分析
CPU
# 执行CPU性能分析，会默认从当前开始执行30scpu采样。
$ go tool pprof http://localhost:6060/debug/pprof/profile
# 也可以通过参数 seconds 指定采样时间。
$ go tool pprof http://localhost:6060/debug/pprof/profile\?seconds=60
# 采样结束后默认进入命令行界面
Fetching profile over HTTP from http://localhost:6060/debug/pprof/profile
Saved profile in /home/user/pprof/pprof.-.samples.cpu.001.pb.gz
File: -
Type: cpu
Time: Dec 24, 2020 at 6:24pm (CST)
Duration: 30.06s, Total samples = 590ms ( 1.96%)
Entering interactive mode (type "help" for commands, "o" for options)
(pprof)
(pprof) top
Showing nodes accounting for 250ms, 42.37% of 590ms total
Showing top 10 nodes out of 285
flat flat% sum% cum cum%
50ms 8.47% 8.47% 50ms 8.47% runtime.futex
30ms 5.08% 13.56% 100ms 16.95% runtime.findrunnable
30ms 5.08% 18.64% 30ms 5.08% syscall.Syscall
20ms 3.39% 22.03% 20ms 3.39% aeshashbody
20ms 3.39% 25.42% 20ms 3.39% encoding/json.(*decodeState).rescanLiteral
20ms 3.39% 28.81% 30ms 5.08% encoding/json.checkValid
20ms 3.39% 32.20% 20ms 3.39% runtime.epollwait
20ms 3.39% 35.59% 30ms 5.08% runtime.gentraceback
20ms 3.39% 38.98% 20ms 3.39% runtime.memclrNoHeapPointers
20ms 3.39% 42.37% 20ms 3.39% runtime.memmove
flat：函数上运行耗时
flat%：函数上运行耗时 总比例
sum%：函数累积使用 CPU 时间比例
cum：函数及之上的调用运行总耗时
cum%：函数及之上的调用运行总耗时比例
内存
更方便的场景为使用web的交互页面代替命令行页面。与cpu性能分析相同，进行内存占用分析。
# 在当前机器 8080 端口运行pprof heap分析。
go tool pprof -http :8080 http://localhost:6060/debug/pprof/heap
