1125064645637738496

2026-08-27 19:32:03 -04:00
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+---
+title: "@SebAaltonen @stewartmoss , nice code up above."
+type: archive
+source: twitter
+source_url: "https://x.com/AndrewJacksonZA/status/1125101399258353665"
+author: "Andrew Jackson"
+handle: AndrewJacksonZA
+post_id: "1125101399258353665"
+date: 2019-05-05
+archived: 2026-08-27
+draft: false
+tags:
+  - archive
+  - twitter
+  - SebAaltonen
+description: "@SebAaltonen @stewartmoss , nice code up above."
+in_reply_to: ""
+parent_post_id: "1125067183476944896"
+---
+
+## Source
+
+- URL: https://x.com/AndrewJacksonZA/status/1125101399258353665
+- Author: Andrew Jackson (@AndrewJacksonZA)
+- Posted: 2019-05-05 18:14:11
+
+## Branch
+
+**1/** **@AndrewJacksonZA** ^1125101399258353665
+
+**@SebAaltonen** **@stewartmoss**
+
+, nice code up above.
+
+Also: https://x.com/SebAaltonen/status/1125075962524262403
+
+/CC @STEMsubsistence and @KeithPlaysPC , because exposure to/learning cool out-of-one's-depth stuff is sometimes extremely valuable. :-)
+
+## Related
+
+- Spine: [[archive/threads/SebAaltonen/2019-05-05-this-is-how-you-write-a-good-x64-spinlock-use-two]]
@@ -0,0 +1,37 @@
+---
+title: "@SebAaltonen It's missing exponential backoff for mm_pause though"
+type: archive
+source: twitter
+source_url: "https://x.com/lectem/status/1125076786520514563"
+author: "Clément Grégoire"
+handle: lectem
+post_id: "1125076786520514563"
+date: 2019-05-05
+archived: 2026-08-27
+draft: false
+tags:
+  - archive
+  - twitter
+  - SebAaltonen
+description: "@SebAaltonen It's missing exponential backoff for mm_pause though"
+in_reply_to: ""
+parent_post_id: "1125067183476944896"
+---
+
+## Source
+
+- URL: https://x.com/lectem/status/1125076786520514563
+- Author: Clément Grégoire (@lectem)
+- Posted: 2019-05-05 16:36:23
+
+## Branch
+
+**1/** **@lectem** ^1125076786520514563
+
+**@SebAaltonen**
+
+It's missing exponential backoff for mm_pause though
+
+## Related
+
+- Spine: [[archive/threads/SebAaltonen/2019-05-05-this-is-how-you-write-a-good-x64-spinlock-use-two]]
@@ -0,0 +1,44 @@
+---
+title: "This is how you write a good x64 spinlock: Use two stage construct."
+type: archive
+source: twitter
+source_url: "https://x.com/SebAaltonen/status/1125064645637738496"
+author: "Sebastian Aaltonen"
+handle: SebAaltonen
+post_id: "1125064645637738496"
+date: 2019-05-05
+archived: 2026-08-27
+draft: false
+tags:
+  - archive
+  - twitter
+  - SebAaltonen
+description: "This is how you write a good x64 spinlock: Use two stage construct."
+in_reply_to: ""
+---
+
+## Source
+
+- URL: https://x.com/SebAaltonen/status/1125064645637738496
+- Author: Sebastian Aaltonen (@SebAaltonen)
+- Posted: 2019-05-05 15:48:08
+
+## Thread
+
+**1/** **@SebAaltonen** ^1125064645637738496
+
+This is how you write a good x64 spinlock: Use two stage construct. Outer test is read. Multiple cores reading same cache line = no contention. Inner = exchange instead of CAS. Pause instruction in the loop body to save power and/or give all cycles to other logical core (SMT).
+
+![](https://pbs.twimg.com/media/D50IVH0W0AALQ0y?format=jpg&name=orig)
+
+**2/** **@SebAaltonen** ^1125065316650889217
+
+Don’t use spinlock for waits. Use spinlock only to guard something that is guaranteed to return quickly. If you have an operation that is often fast but sometimes slow, use two stage spinlock with internal OS mutex.
+
+**3/** **@SebAaltonen** ^1125067183476944896
+
+Naive (bad) vs optimized (good) performance. See above post for code.
+
+![](https://pbs.twimg.com/media/D50Ko4mXoAAR97L?format=jpg&name=orig)
+
+Branches: [[archive/threads/SebAaltonen/2019-05-05-this-is-how-you-write-a-good-x64-spinlock-use-two/2019-05-05-lectem-its-missing-exponential-backoff-for-mm-pause]], [[archive/threads/SebAaltonen/2019-05-05-this-is-how-you-write-a-good-x64-spinlock-use-two/2019-05-05-AndrewJacksonZA-nice-code-up-above-also-https-x-com-sebaaltonen]]
@@ -9,7 +9,9 @@ tags:
  - SebAaltonen
 ---

+- [[archive/threads/SebAaltonen/2018-12-29-i-wish-i-was-as-productive-blogger-as-aras-p]]
 - [[archive/threads/SebAaltonen/2019-01-01-now-that-people-have-already-said-highly]]
+- [[archive/threads/SebAaltonen/2019-05-05-this-is-how-you-write-a-good-x64-spinlock-use-two]]
 - [[archive/threads/SebAaltonen/2022-11-22-ive-long-time-talked-about-killing-the-graphics]]
 - [[archive/threads/SebAaltonen/2024-04-04-this-is-how-slow-code-feels-like]]
 - [[archive/threads/SebAaltonen/2024-05-03-why-should-one-be-able-to-code-without]]