Maybe spin-waits in the thread pool can be tuned better for arm/arm64 #39559

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#57885
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Maybe spin-waits in the thread pool can be tuned better for arm/arm64#39559
#57885
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arch-arm64area-System.Threading
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7.0.0

Description

@kouvel
kouvel
opened on Jul 17, 2020
  • The yield instruction has a very short delay on some machines and may also be implemented as a NOP
  • In bursty scenarios relatively more time is spent in Sleep(0) / sched_yield, relatively little in the yield loop, and relatively a lot more time spent in swapper
  • In ASP.NET when a low number of connections is used such that CPU usage is squarely less than 100%, there is a sudden and disproportional drop in RPS, sudden increase in latency, and relatively much larger amount of time spent in swapper. This could be because of the above two, when little time is spent yielding and all ready threads are already scheduled, the spin-wait can complete very quickly and trigger a wait.
  • Requesting fewer threads in the thread pool appears to trigger the issue at slightly higher number of connections because fewer thread requests are coming in to prevent threads from triggering a wait. Some tests changing the spin-waiting model to that used in x86/x64 with larger spin counts showed to compensate for the issue mostly, but with some small tradeoffs.

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      , '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" + '

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      Maybe spin-waits in the thread pool can be tuned better for arm/arm64 #39559
      Closed
      #57885
      Closed
      Maybe spin-waits in the thread pool can be tuned better for arm/arm64#39559
      #57885
      Labels
      arch-arm64area-System.Threading
      Milestone
      7.0.0
      Description
      @kouvel
      kouvel
      opened on Jul 17, 2020
      • The yield instruction has a very short delay on some machines and may also be implemented as a NOP
      • In bursty scenarios relatively more time is spent in Sleep(0) / sched_yield, relatively little in the yield loop, and relatively a lot more time spent in swapper
      • In ASP.NET when a low number of connections is used such that CPU usage is squarely less than 100%, there is a sudden and disproportional drop in RPS, sudden increase in latency, and relatively much larger amount of time spent in swapper. This could be because of the above two, when little time is spent yielding and all ready threads are already scheduled, the spin-wait can complete very quickly and trigger a wait.
      • Requesting fewer threads in the thread pool appears to trigger the issue at slightly higher number of connections because fewer thread requests are coming in to prevent threads from triggering a wait. Some tests changing the spin-waiting model to that used in x86/x64 with larger spin counts showed to compensate for the issue mostly, but with some small tradeoffs.
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, '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
          Maybe spin-waits in the thread pool can be tuned better for arm/arm64 #39559
          Closed
          #57885
          Closed
          Maybe spin-waits in the thread pool can be tuned better for arm/arm64#39559
          #57885
          Labels
          arch-arm64area-System.Threading
          Milestone
          7.0.0
          Description
          @kouvel
          kouvel
          opened on Jul 17, 2020
          • The yield instruction has a very short delay on some machines and may also be implemented as a NOP
          • In bursty scenarios relatively more time is spent in Sleep(0) / sched_yield, relatively little in the yield loop, and relatively a lot more time spent in swapper
          • In ASP.NET when a low number of connections is used such that CPU usage is squarely less than 100%, there is a sudden and disproportional drop in RPS, sudden increase in latency, and relatively much larger amount of time spent in swapper. This could be because of the above two, when little time is spent yielding and all ready threads are already scheduled, the spin-wait can complete very quickly and trigger a wait.
          • Requesting fewer threads in the thread pool appears to trigger the issue at slightly higher number of connections because fewer thread requests are coming in to prevent threads from triggering a wait. Some tests changing the spin-waiting model to that used in x86/x64 with larger spin counts showed to compensate for the issue mostly, but with some small tradeoffs.
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, '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
              Maybe spin-waits in the thread pool can be tuned better for arm/arm64 #39559
              Closed
              #57885
              Closed
              Maybe spin-waits in the thread pool can be tuned better for arm/arm64#39559
              #57885
              Labels
              arch-arm64area-System.Threading
              Milestone
              7.0.0
              Description
              @kouvel
              kouvel
              opened on Jul 17, 2020
              • The yield instruction has a very short delay on some machines and may also be implemented as a NOP
              • In bursty scenarios relatively more time is spent in Sleep(0) / sched_yield, relatively little in the yield loop, and relatively a lot more time spent in swapper
              • In ASP.NET when a low number of connections is used such that CPU usage is squarely less than 100%, there is a sudden and disproportional drop in RPS, sudden increase in latency, and relatively much larger amount of time spent in swapper. This could be because of the above two, when little time is spent yielding and all ready threads are already scheduled, the spin-wait can complete very quickly and trigger a wait.
              • Requesting fewer threads in the thread pool appears to trigger the issue at slightly higher number of connections because fewer thread requests are coming in to prevent threads from triggering a wait. Some tests changing the spin-waiting model to that used in x86/x64 with larger spin counts showed to compensate for the issue mostly, but with some small tradeoffs.
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, '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" + '

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                  Maybe spin-waits in the thread pool can be tuned better for arm/arm64 #39559
                  Closed
                  #57885
                  Closed
                  Maybe spin-waits in the thread pool can be tuned better for arm/arm64#39559
                  #57885
                  Labels
                  arch-arm64area-System.Threading
                  Milestone
                  7.0.0
                  Description
                  @kouvel
                  kouvel
                  opened on Jul 17, 2020
                  • The yield instruction has a very short delay on some machines and may also be implemented as a NOP
                  • In bursty scenarios relatively more time is spent in Sleep(0) / sched_yield, relatively little in the yield loop, and relatively a lot more time spent in swapper
                  • In ASP.NET when a low number of connections is used such that CPU usage is squarely less than 100%, there is a sudden and disproportional drop in RPS, sudden increase in latency, and relatively much larger amount of time spent in swapper. This could be because of the above two, when little time is spent yielding and all ready threads are already scheduled, the spin-wait can complete very quickly and trigger a wait.
                  • Requesting fewer threads in the thread pool appears to trigger the issue at slightly higher number of connections because fewer thread requests are coming in to prevent threads from triggering a wait. Some tests changing the spin-waiting model to that used in x86/x64 with larger spin counts showed to compensate for the issue mostly, but with some small tradeoffs.
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                      None yet
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, '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('^' + ".*" + '

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                      Maybe spin-waits in the thread pool can be tuned better for arm/arm64 #39559
                      Closed
                      #57885
                      Closed
                      Maybe spin-waits in the thread pool can be tuned better for arm/arm64#39559
                      #57885
                      Labels
                      arch-arm64area-System.Threading
                      Milestone
                      7.0.0
                      Description
                      @kouvel
                      kouvel
                      opened on Jul 17, 2020
                      • The yield instruction has a very short delay on some machines and may also be implemented as a NOP
                      • In bursty scenarios relatively more time is spent in Sleep(0) / sched_yield, relatively little in the yield loop, and relatively a lot more time spent in swapper
                      • In ASP.NET when a low number of connections is used such that CPU usage is squarely less than 100%, there is a sudden and disproportional drop in RPS, sudden increase in latency, and relatively much larger amount of time spent in swapper. This could be because of the above two, when little time is spent yielding and all ready threads are already scheduled, the spin-wait can complete very quickly and trigger a wait.
                      • Requesting fewer threads in the thread pool appears to trigger the issue at slightly higher number of connections because fewer thread requests are coming in to prevent threads from triggering a wait. Some tests changing the spin-waiting model to that used in x86/x64 with larger spin counts showed to compensate for the issue mostly, but with some small tradeoffs.
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, '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
                          Maybe spin-waits in the thread pool can be tuned better for arm/arm64 #39559
                          Closed
                          #57885
                          Closed
                          Maybe spin-waits in the thread pool can be tuned better for arm/arm64#39559
                          #57885
                          Labels
                          arch-arm64area-System.Threading
                          Milestone
                          7.0.0
                          Description
                          @kouvel
                          kouvel
                          opened on Jul 17, 2020
                          • The yield instruction has a very short delay on some machines and may also be implemented as a NOP
                          • In bursty scenarios relatively more time is spent in Sleep(0) / sched_yield, relatively little in the yield loop, and relatively a lot more time spent in swapper
                          • In ASP.NET when a low number of connections is used such that CPU usage is squarely less than 100%, there is a sudden and disproportional drop in RPS, sudden increase in latency, and relatively much larger amount of time spent in swapper. This could be because of the above two, when little time is spent yielding and all ready threads are already scheduled, the spin-wait can complete very quickly and trigger a wait.
                          • Requesting fewer threads in the thread pool appears to trigger the issue at slightly higher number of connections because fewer thread requests are coming in to prevent threads from triggering a wait. Some tests changing the spin-waiting model to that used in x86/x64 with larger spin counts showed to compensate for the issue mostly, but with some small tradeoffs.
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, '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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                              Maybe spin-waits in the thread pool can be tuned better for arm/arm64 #39559
                              Closed
                              #57885
                              Closed
                              Maybe spin-waits in the thread pool can be tuned better for arm/arm64#39559
                              #57885
                              Labels
                              arch-arm64area-System.Threading
                              Milestone
                              7.0.0
                              Description
                              @kouvel
                              kouvel
                              opened on Jul 17, 2020
                              • The yield instruction has a very short delay on some machines and may also be implemented as a NOP
                              • In bursty scenarios relatively more time is spent in Sleep(0) / sched_yield, relatively little in the yield loop, and relatively a lot more time spent in swapper
                              • In ASP.NET when a low number of connections is used such that CPU usage is squarely less than 100%, there is a sudden and disproportional drop in RPS, sudden increase in latency, and relatively much larger amount of time spent in swapper. This could be because of the above two, when little time is spent yielding and all ready threads are already scheduled, the spin-wait can complete very quickly and trigger a wait.
                              • Requesting fewer threads in the thread pool appears to trigger the issue at slightly higher number of connections because fewer thread requests are coming in to prevent threads from triggering a wait. Some tests changing the spin-waiting model to that used in x86/x64 with larger spin counts showed to compensate for the issue mostly, but with some small tradeoffs.
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