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Myths Programmers Believe about CPU Caches (2018)

Myths Programmers Believe about CPU Caches (2018)

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·October 31, 2025
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QuaternionsBhop

Since the CPU is doing cache coherency transparently, perhaps there should be some sort of way to promise that an application is well-behaved in order to access a lower-level non-transparent instruction set to manually manage the cache coherency from the application level. Or perhaps applications can never be trusted with that level of control over the hardware. The MESI model reminded me of Rust's ownership and borrowing. The pattern also appears in OpenGL vs Vulkan drivers, implicit sync vs explicit sync. Yet another example would be the cache management work involved in squeezing out maximum throughput CUDA on an enterprise GPU.

breppp

Very interesting, I am hardly an expert, but this gives the impression that if only without that meddling software we will all live in a synchronous world.

This ignores store buffers and consequently memory fencing which is the basis for the nightmarish std::memory_order, the worst api documentation you will ever meet

yohbho

2018, discussed on HN in 2023: https://news.ycombinator.com/item?id=36333034

  Myths Programmers Believe about CPU Caches (2018) (rajivprab.com)
 176 points by whack on June 14, 2023 | hide | past | favorite | 138 comments