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PerfJ

Join the chat at https://gitter.im/coderplay/perfj

PerfJ is a wrapper of linux perf for java programs.

As Brendan Gregg's words

In order to profile java programs, you need a profiler that can sample stack traces. There has historically been two types of profilers:

  • System profilers: like Linux perf, which shows system code paths (eg, JVM GC, syscalls, TCP), but not Java methods.
  • JVM profilers: like hprof, LJP, and commercial profilers. These show Java methods, but usually not system code paths.

Ideally, we need a profile result that does it all: system and Java code paths. Apart from convenience, it also shows system code-paths in Java context, which can be crucial for understanding a profile properly.

The problem is getting a system profiler to understand Java methods and stack traces. If you try Linux perf_events, for example, you'll see hexadecimal numbers and broken stack traces, as it can't convert addresses into Java symbols, and can't walk the JVM stack.

There are two specific problems:

  • The JVM compiles methods on the fly (just-in-time: JIT), and doesn't expose a traditional symbol table for system profilers to read.
  • The JVM also uses the frame pointer register (RBP on x86-64) as a general purpose register, breaking traditional stack walking.

Thanks to the work by Brendan Gregg and Zoltan Majo. We will have an option to turn on the preservation of frame pointer on JDK 8u60+.

This project is based on Johannes Rudolph's work at here, but PerfJ is more convenient and safer to use.

PerfJ can produce flame graph through Brendan Gregg's FlameGraph tool .

Below is an example shows the hotspot of a pure java leveldb program. Green is Java layer, yellow is JVM layer, and red is system layer(native user-level, or kernel). Longer bar means higher cpu percentage.

PerfJ CPU Flame Graph Example

There is a raw interactive SVG image [here] (http://blog.minzhou.info/perfj/perfj.svg).

Prerequisites

  • Linux x86_64
  • perf
  • JDK 8u60 and higher

Build

Before starting building PerfJ, make sure gcc is already installed.

checkout the source from github

git clone https://github.com/coderplay/perfj.git

and run below in the future building

cd perfj
./gradlew releaseTarGz

Installation

Before install PerfJ, you should install Linux perf first

To install perf on centos/redhat/fedora linux system

yum install perf.x86_64

To install perf on ubuntu linux system

apt-get install linux-tools-common linux-tools-generic linux-tools-`uname -r`

then download perfj-*.tgz from the [release page] (https://github.com/coderplay/perfj/releases), untar it

tar zxvf perf-*.tgz

Usage

Check the [wiki pages] (https://github.com/coderplay/perfj/wiki)

License

This library is licensed under GPLv2. See the LICENSE file.

About

PerfJ is a wrapper of linux perf for java programs.

Resources

Readme
GPL-2.0 license
Activity

Stars

354 stars

Watchers

49 watching

Forks

51 forks
Report repository

Releases

Packages

Used by

Contributors

Languages

, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
BranchesTags
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PerfJ
Join the chat at https://gitter.im/coderplay/perfj
PerfJ is a wrapper of linux perf for java programs.
As Brendan Gregg's words
In order to profile java programs, you need a profiler that can sample stack traces. There has historically been two types of profilers:
  • System profilers: like Linux perf, which shows system code paths (eg, JVM GC, syscalls, TCP), but not Java methods.
  • JVM profilers: like hprof, LJP, and commercial profilers. These show Java methods, but usually not system code paths.
Ideally, we need a profile result that does it all: system and Java code paths. Apart from convenience, it also shows system code-paths in Java context, which can be crucial for understanding a profile properly.
The problem is getting a system profiler to understand Java methods and stack traces. If you try Linux perf_events, for example, you'll see hexadecimal numbers and broken stack traces, as it can't convert addresses into Java symbols, and can't walk the JVM stack.
There are two specific problems:
  • The JVM compiles methods on the fly (just-in-time: JIT), and doesn't expose a traditional symbol table for system profilers to read.
  • The JVM also uses the frame pointer register (RBP on x86-64) as a general purpose register, breaking traditional stack walking.
Thanks to the work by Brendan Gregg and Zoltan Majo. We will have an option to turn on the preservation of frame pointer on JDK 8u60+.
This project is based on Johannes Rudolph's work at here, but PerfJ is more convenient and safer to use.
PerfJ can produce flame graph through Brendan Gregg's FlameGraph tool .
Below is an example shows the hotspot of a pure java leveldb program. Green is Java layer, yellow is JVM layer, and red is system layer(native user-level, or kernel). Longer bar means higher cpu percentage.
PerfJ CPU Flame Graph Example
There is a raw interactive SVG image [here] (http://blog.minzhou.info/perfj/perfj.svg).
Prerequisites
  • Linux x86_64
  • perf
  • JDK 8u60 and higher
Build
Before starting building PerfJ, make sure gcc is already installed.
checkout the source from github
git clone https://github.com/coderplay/perfj.git

and run below in the future building
cd perfj
./gradlew releaseTarGz

Installation
Before install PerfJ, you should install Linux perf first
To install perf on centos/redhat/fedora linux system
yum install perf.x86_64

To install perf on ubuntu linux system
apt-get install linux-tools-common linux-tools-generic linux-tools-`uname -r`

then download perfj-*.tgz from the [release page] (https://github.com/coderplay/perfj/releases), untar it
tar zxvf perf-*.tgz

Usage
Check the [wiki pages] (https://github.com/coderplay/perfj/wiki)
License
This library is licensed under GPLv2. See the LICENSE file.
About
PerfJ is a wrapper of linux perf for java programs.
Resources
Readme
GPL-2.0 license
Activity
Stars
354 stars
Watchers
49 watching
Forks
51 forks
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
BranchesTags
Repository files navigation
PerfJ
Join the chat at https://gitter.im/coderplay/perfj
PerfJ is a wrapper of linux perf for java programs.
As Brendan Gregg's words
In order to profile java programs, you need a profiler that can sample stack traces. There has historically been two types of profilers:
  • System profilers: like Linux perf, which shows system code paths (eg, JVM GC, syscalls, TCP), but not Java methods.
  • JVM profilers: like hprof, LJP, and commercial profilers. These show Java methods, but usually not system code paths.
Ideally, we need a profile result that does it all: system and Java code paths. Apart from convenience, it also shows system code-paths in Java context, which can be crucial for understanding a profile properly.
The problem is getting a system profiler to understand Java methods and stack traces. If you try Linux perf_events, for example, you'll see hexadecimal numbers and broken stack traces, as it can't convert addresses into Java symbols, and can't walk the JVM stack.
There are two specific problems:
  • The JVM compiles methods on the fly (just-in-time: JIT), and doesn't expose a traditional symbol table for system profilers to read.
  • The JVM also uses the frame pointer register (RBP on x86-64) as a general purpose register, breaking traditional stack walking.
Thanks to the work by Brendan Gregg and Zoltan Majo. We will have an option to turn on the preservation of frame pointer on JDK 8u60+.
This project is based on Johannes Rudolph's work at here, but PerfJ is more convenient and safer to use.
PerfJ can produce flame graph through Brendan Gregg's FlameGraph tool .
Below is an example shows the hotspot of a pure java leveldb program. Green is Java layer, yellow is JVM layer, and red is system layer(native user-level, or kernel). Longer bar means higher cpu percentage.
PerfJ CPU Flame Graph Example
There is a raw interactive SVG image [here] (http://blog.minzhou.info/perfj/perfj.svg).
Prerequisites
  • Linux x86_64
  • perf
  • JDK 8u60 and higher
Build
Before starting building PerfJ, make sure gcc is already installed.
checkout the source from github
git clone https://github.com/coderplay/perfj.git

and run below in the future building
cd perfj
./gradlew releaseTarGz

Installation
Before install PerfJ, you should install Linux perf first
To install perf on centos/redhat/fedora linux system
yum install perf.x86_64

To install perf on ubuntu linux system
apt-get install linux-tools-common linux-tools-generic linux-tools-`uname -r`

then download perfj-*.tgz from the [release page] (https://github.com/coderplay/perfj/releases), untar it
tar zxvf perf-*.tgz

Usage
Check the [wiki pages] (https://github.com/coderplay/perfj/wiki)
License
This library is licensed under GPLv2. See the LICENSE file.
About
PerfJ is a wrapper of linux perf for java programs.
Resources
Readme
GPL-2.0 license
Activity
Stars
354 stars
Watchers
49 watching
Forks
51 forks
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
BranchesTags
Repository files navigation
PerfJ
Join the chat at https://gitter.im/coderplay/perfj
PerfJ is a wrapper of linux perf for java programs.
As Brendan Gregg's words
In order to profile java programs, you need a profiler that can sample stack traces. There has historically been two types of profilers:
  • System profilers: like Linux perf, which shows system code paths (eg, JVM GC, syscalls, TCP), but not Java methods.
  • JVM profilers: like hprof, LJP, and commercial profilers. These show Java methods, but usually not system code paths.
Ideally, we need a profile result that does it all: system and Java code paths. Apart from convenience, it also shows system code-paths in Java context, which can be crucial for understanding a profile properly.
The problem is getting a system profiler to understand Java methods and stack traces. If you try Linux perf_events, for example, you'll see hexadecimal numbers and broken stack traces, as it can't convert addresses into Java symbols, and can't walk the JVM stack.
There are two specific problems:
  • The JVM compiles methods on the fly (just-in-time: JIT), and doesn't expose a traditional symbol table for system profilers to read.
  • The JVM also uses the frame pointer register (RBP on x86-64) as a general purpose register, breaking traditional stack walking.
Thanks to the work by Brendan Gregg and Zoltan Majo. We will have an option to turn on the preservation of frame pointer on JDK 8u60+.
This project is based on Johannes Rudolph's work at here, but PerfJ is more convenient and safer to use.
PerfJ can produce flame graph through Brendan Gregg's FlameGraph tool .
Below is an example shows the hotspot of a pure java leveldb program. Green is Java layer, yellow is JVM layer, and red is system layer(native user-level, or kernel). Longer bar means higher cpu percentage.
PerfJ CPU Flame Graph Example
There is a raw interactive SVG image [here] (http://blog.minzhou.info/perfj/perfj.svg).
Prerequisites
  • Linux x86_64
  • perf
  • JDK 8u60 and higher
Build
Before starting building PerfJ, make sure gcc is already installed.
checkout the source from github
git clone https://github.com/coderplay/perfj.git

and run below in the future building
cd perfj
./gradlew releaseTarGz

Installation
Before install PerfJ, you should install Linux perf first
To install perf on centos/redhat/fedora linux system
yum install perf.x86_64

To install perf on ubuntu linux system
apt-get install linux-tools-common linux-tools-generic linux-tools-`uname -r`

then download perfj-*.tgz from the [release page] (https://github.com/coderplay/perfj/releases), untar it
tar zxvf perf-*.tgz

Usage
Check the [wiki pages] (https://github.com/coderplay/perfj/wiki)
License
This library is licensed under GPLv2. See the LICENSE file.
About
PerfJ is a wrapper of linux perf for java programs.
Resources
Readme
GPL-2.0 license
Activity
Stars
354 stars
Watchers
49 watching
Forks
51 forks
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
BranchesTags
Repository files navigation
PerfJ
Join the chat at https://gitter.im/coderplay/perfj
PerfJ is a wrapper of linux perf for java programs.
As Brendan Gregg's words
In order to profile java programs, you need a profiler that can sample stack traces. There has historically been two types of profilers:
  • System profilers: like Linux perf, which shows system code paths (eg, JVM GC, syscalls, TCP), but not Java methods.
  • JVM profilers: like hprof, LJP, and commercial profilers. These show Java methods, but usually not system code paths.
Ideally, we need a profile result that does it all: system and Java code paths. Apart from convenience, it also shows system code-paths in Java context, which can be crucial for understanding a profile properly.
The problem is getting a system profiler to understand Java methods and stack traces. If you try Linux perf_events, for example, you'll see hexadecimal numbers and broken stack traces, as it can't convert addresses into Java symbols, and can't walk the JVM stack.
There are two specific problems:
  • The JVM compiles methods on the fly (just-in-time: JIT), and doesn't expose a traditional symbol table for system profilers to read.
  • The JVM also uses the frame pointer register (RBP on x86-64) as a general purpose register, breaking traditional stack walking.
Thanks to the work by Brendan Gregg and Zoltan Majo. We will have an option to turn on the preservation of frame pointer on JDK 8u60+.
This project is based on Johannes Rudolph's work at here, but PerfJ is more convenient and safer to use.
PerfJ can produce flame graph through Brendan Gregg's FlameGraph tool .
Below is an example shows the hotspot of a pure java leveldb program. Green is Java layer, yellow is JVM layer, and red is system layer(native user-level, or kernel). Longer bar means higher cpu percentage.
PerfJ CPU Flame Graph Example
There is a raw interactive SVG image [here] (http://blog.minzhou.info/perfj/perfj.svg).
Prerequisites
  • Linux x86_64
  • perf
  • JDK 8u60 and higher
Build
Before starting building PerfJ, make sure gcc is already installed.
checkout the source from github
git clone https://github.com/coderplay/perfj.git

and run below in the future building
cd perfj
./gradlew releaseTarGz

Installation
Before install PerfJ, you should install Linux perf first
To install perf on centos/redhat/fedora linux system
yum install perf.x86_64

To install perf on ubuntu linux system
apt-get install linux-tools-common linux-tools-generic linux-tools-`uname -r`

then download perfj-*.tgz from the [release page] (https://github.com/coderplay/perfj/releases), untar it
tar zxvf perf-*.tgz

Usage
Check the [wiki pages] (https://github.com/coderplay/perfj/wiki)
License
This library is licensed under GPLv2. See the LICENSE file.
About
PerfJ is a wrapper of linux perf for java programs.
Resources
Readme
GPL-2.0 license
Activity
Stars
354 stars
Watchers
49 watching
Forks
51 forks
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
BranchesTags
Repository files navigation
PerfJ
Join the chat at https://gitter.im/coderplay/perfj
PerfJ is a wrapper of linux perf for java programs.
As Brendan Gregg's words
In order to profile java programs, you need a profiler that can sample stack traces. There has historically been two types of profilers:
  • System profilers: like Linux perf, which shows system code paths (eg, JVM GC, syscalls, TCP), but not Java methods.
  • JVM profilers: like hprof, LJP, and commercial profilers. These show Java methods, but usually not system code paths.
Ideally, we need a profile result that does it all: system and Java code paths. Apart from convenience, it also shows system code-paths in Java context, which can be crucial for understanding a profile properly.
The problem is getting a system profiler to understand Java methods and stack traces. If you try Linux perf_events, for example, you'll see hexadecimal numbers and broken stack traces, as it can't convert addresses into Java symbols, and can't walk the JVM stack.
There are two specific problems:
  • The JVM compiles methods on the fly (just-in-time: JIT), and doesn't expose a traditional symbol table for system profilers to read.
  • The JVM also uses the frame pointer register (RBP on x86-64) as a general purpose register, breaking traditional stack walking.
Thanks to the work by Brendan Gregg and Zoltan Majo. We will have an option to turn on the preservation of frame pointer on JDK 8u60+.
This project is based on Johannes Rudolph's work at here, but PerfJ is more convenient and safer to use.
PerfJ can produce flame graph through Brendan Gregg's FlameGraph tool .
Below is an example shows the hotspot of a pure java leveldb program. Green is Java layer, yellow is JVM layer, and red is system layer(native user-level, or kernel). Longer bar means higher cpu percentage.
PerfJ CPU Flame Graph Example
There is a raw interactive SVG image [here] (http://blog.minzhou.info/perfj/perfj.svg).
Prerequisites
  • Linux x86_64
  • perf
  • JDK 8u60 and higher
Build
Before starting building PerfJ, make sure gcc is already installed.
checkout the source from github
git clone https://github.com/coderplay/perfj.git

and run below in the future building
cd perfj
./gradlew releaseTarGz

Installation
Before install PerfJ, you should install Linux perf first
To install perf on centos/redhat/fedora linux system
yum install perf.x86_64

To install perf on ubuntu linux system
apt-get install linux-tools-common linux-tools-generic linux-tools-`uname -r`

then download perfj-*.tgz from the [release page] (https://github.com/coderplay/perfj/releases), untar it
tar zxvf perf-*.tgz

Usage
Check the [wiki pages] (https://github.com/coderplay/perfj/wiki)
License
This library is licensed under GPLv2. See the LICENSE file.
About
PerfJ is a wrapper of linux perf for java programs.
Resources
Readme
GPL-2.0 license
Activity
Stars
354 stars
Watchers
49 watching
Forks
51 forks
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
BranchesTags
Repository files navigation
PerfJ
Join the chat at https://gitter.im/coderplay/perfj
PerfJ is a wrapper of linux perf for java programs.
As Brendan Gregg's words
In order to profile java programs, you need a profiler that can sample stack traces. There has historically been two types of profilers:
  • System profilers: like Linux perf, which shows system code paths (eg, JVM GC, syscalls, TCP), but not Java methods.
  • JVM profilers: like hprof, LJP, and commercial profilers. These show Java methods, but usually not system code paths.
Ideally, we need a profile result that does it all: system and Java code paths. Apart from convenience, it also shows system code-paths in Java context, which can be crucial for understanding a profile properly.
The problem is getting a system profiler to understand Java methods and stack traces. If you try Linux perf_events, for example, you'll see hexadecimal numbers and broken stack traces, as it can't convert addresses into Java symbols, and can't walk the JVM stack.
There are two specific problems:
  • The JVM compiles methods on the fly (just-in-time: JIT), and doesn't expose a traditional symbol table for system profilers to read.
  • The JVM also uses the frame pointer register (RBP on x86-64) as a general purpose register, breaking traditional stack walking.
Thanks to the work by Brendan Gregg and Zoltan Majo. We will have an option to turn on the preservation of frame pointer on JDK 8u60+.
This project is based on Johannes Rudolph's work at here, but PerfJ is more convenient and safer to use.
PerfJ can produce flame graph through Brendan Gregg's FlameGraph tool .
Below is an example shows the hotspot of a pure java leveldb program. Green is Java layer, yellow is JVM layer, and red is system layer(native user-level, or kernel). Longer bar means higher cpu percentage.
PerfJ CPU Flame Graph Example
There is a raw interactive SVG image [here] (http://blog.minzhou.info/perfj/perfj.svg).
Prerequisites
  • Linux x86_64
  • perf
  • JDK 8u60 and higher
Build
Before starting building PerfJ, make sure gcc is already installed.
checkout the source from github
git clone https://github.com/coderplay/perfj.git

and run below in the future building
cd perfj
./gradlew releaseTarGz

Installation
Before install PerfJ, you should install Linux perf first
To install perf on centos/redhat/fedora linux system
yum install perf.x86_64

To install perf on ubuntu linux system
apt-get install linux-tools-common linux-tools-generic linux-tools-`uname -r`

then download perfj-*.tgz from the [release page] (https://github.com/coderplay/perfj/releases), untar it
tar zxvf perf-*.tgz

Usage
Check the [wiki pages] (https://github.com/coderplay/perfj/wiki)
License
This library is licensed under GPLv2. See the LICENSE file.
About
PerfJ is a wrapper of linux perf for java programs.
Resources
Readme
GPL-2.0 license
Activity
Stars
354 stars
Watchers
49 watching
Forks
51 forks
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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PerfJ
Join the chat at https://gitter.im/coderplay/perfj
PerfJ is a wrapper of linux perf for java programs.
As Brendan Gregg's words
In order to profile java programs, you need a profiler that can sample stack traces. There has historically been two types of profilers:
  • System profilers: like Linux perf, which shows system code paths (eg, JVM GC, syscalls, TCP), but not Java methods.
  • JVM profilers: like hprof, LJP, and commercial profilers. These show Java methods, but usually not system code paths.
Ideally, we need a profile result that does it all: system and Java code paths. Apart from convenience, it also shows system code-paths in Java context, which can be crucial for understanding a profile properly.
The problem is getting a system profiler to understand Java methods and stack traces. If you try Linux perf_events, for example, you'll see hexadecimal numbers and broken stack traces, as it can't convert addresses into Java symbols, and can't walk the JVM stack.
There are two specific problems:
  • The JVM compiles methods on the fly (just-in-time: JIT), and doesn't expose a traditional symbol table for system profilers to read.
  • The JVM also uses the frame pointer register (RBP on x86-64) as a general purpose register, breaking traditional stack walking.
Thanks to the work by Brendan Gregg and Zoltan Majo. We will have an option to turn on the preservation of frame pointer on JDK 8u60+.
This project is based on Johannes Rudolph's work at here, but PerfJ is more convenient and safer to use.
PerfJ can produce flame graph through Brendan Gregg's FlameGraph tool .
Below is an example shows the hotspot of a pure java leveldb program. Green is Java layer, yellow is JVM layer, and red is system layer(native user-level, or kernel). Longer bar means higher cpu percentage.
PerfJ CPU Flame Graph Example
There is a raw interactive SVG image [here] (http://blog.minzhou.info/perfj/perfj.svg).
Prerequisites
  • Linux x86_64
  • perf
  • JDK 8u60 and higher
Build
Before starting building PerfJ, make sure gcc is already installed.
checkout the source from github
git clone https://github.com/coderplay/perfj.git

and run below in the future building
cd perfj
./gradlew releaseTarGz

Installation
Before install PerfJ, you should install Linux perf first
To install perf on centos/redhat/fedora linux system
yum install perf.x86_64

To install perf on ubuntu linux system
apt-get install linux-tools-common linux-tools-generic linux-tools-`uname -r`

then download perfj-*.tgz from the [release page] (https://github.com/coderplay/perfj/releases), untar it
tar zxvf perf-*.tgz

Usage
Check the [wiki pages] (https://github.com/coderplay/perfj/wiki)
License
This library is licensed under GPLv2. See the LICENSE file.
About
PerfJ is a wrapper of linux perf for java programs.
Resources
Readme
GPL-2.0 license
Activity
Stars
354 stars
Watchers
49 watching
Forks
51 forks
Report repository
Releases
Packages
Used by
Contributors
Languages