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cacheLineForCpu

atomic.cacheLineForCpu
pub fn cacheLineForCpu(cpu: std.Target.Cpu) u16

File

lib/std/atomic.zig:413

Code

pub fn cacheLineForCpu(cpu: std.Target.Cpu) u16 {
    return switch (cpu.arch) {
        // x86_64: Starting from Intel's Sandy Bridge, the spatial prefetcher pulls in pairs of 64-byte cache lines at a time.
        // - https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-optimization-manual.pdf
        // - https://github.com/facebook/folly/blob/1b5288e6eea6df074758f877c849b6e73bbb9fbb/folly/lang/Align.h#L107
        //
        // aarch64: Some big.LITTLE ARM archs have "big" cores with 128-byte cache lines:
        // - https://www.mono-project.com/news/2016/09/12/arm64-icache/
        // - https://cpufun.substack.com/p/more-m1-fun-hardware-information
        //
        // - https://github.com/torvalds/linux/blob/3a7e02c040b130b5545e4b115aada7bacd80a2b6/arch/arc/Kconfig#L212
        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_ppc64x.go#L9
        .x86_64,
        .aarch64,
        .aarch64_be,
        .arc,
        .arceb,
        .powerpc64,
        .powerpc64le,
        => 128,

        // https://github.com/llvm/llvm-project/blob/e379094328e49731a606304f7e3559d4f1fa96f9/clang/lib/Basic/Targets/Hexagon.h#L145-L151
        .hexagon,
        => if (cpu.has(.hexagon, .v73)) 64 else 32,

        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_arm.go#L7
        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mips.go#L7
        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mipsle.go#L7
        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mips64x.go#L9
        // - https://github.com/torvalds/linux/blob/3a7e02c040b130b5545e4b115aada7bacd80a2b6/arch/sparc/include/asm/cache.h#L14
        // - https://github.com/torvalds/linux/blob/3a7e02c040b130b5545e4b115aada7bacd80a2b6/arch/microblaze/include/asm/cache.h#L15
        // - https://github.com/torvalds/linux/blob/3a7e02c040b130b5545e4b115aada7bacd80a2b6/arch/sh/include/cpu-sh4/cpu/cache.h#L10
        // - https://github.com/openbsd/src/blob/1957873d2063db11dab780eca75b5e629d1e838d/sys/arch/m88k/m88k/atomic.S#L22
        .arm,
        .armeb,
        .thumb,
        .thumbeb,
        .m88k,
        .microblaze,
        .microblazeel,
        .mips,
        .mipsel,
        .mips64,
        .mips64el,
        .sh,
        .sheb,
        .sparc,
        .sparc64,
        => 32,

        // - https://github.com/torvalds/linux/blob/3a7e02c040b130b5545e4b115aada7bacd80a2b6/arch/m68k/include/asm/cache.h#L10
        // - https://github.com/torvalds/linux/blob/3a7e02c040b130b5545e4b115aada7bacd80a2b6/arch/openrisc/include/asm/cache.h#L24
        // - https://github.com/torvalds/linux/blob/3a7e02c040b130b5545e4b115aada7bacd80a2b6/arch/parisc/include/asm/cache.h#L16
        .hppa,
        .hppa64,
        .m68k,
        .or1k,
        => 16,

        // - https://www.ti.com/lit/pdf/slaa498
        .msp430,
        => 8,

        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_s390x.go#L7
        // - https://sxauroratsubasa.sakura.ne.jp/documents/guide/pdfs/Aurora_ISA_guide.pdf
        .s390x,
        .ve,
        => 256,

        // Other x86 and WASM platforms have 64-byte cache lines.
        // The rest of the architectures are assumed to be similar.
        // - https://github.com/golang/go/blob/dda2991c2ea0c5914714469c4defc2562a907230/src/internal/cpu/cpu_x86.go#L9
        // - https://github.com/golang/go/blob/0a9321ad7f8c91e1b0c7184731257df923977eb9/src/internal/cpu/cpu_loong64.go#L11
        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_wasm.go#L7
        // - https://github.com/golang/go/blob/19e923182e590ae6568c2c714f20f32512aeb3e3/src/internal/cpu/cpu_riscv64.go#L7
        // - https://github.com/torvalds/linux/blob/3a7e02c040b130b5545e4b115aada7bacd80a2b6/arch/xtensa/variants/csp/include/variant/core.h#L209
        // - https://github.com/torvalds/linux/blob/3a7e02c040b130b5545e4b115aada7bacd80a2b6/arch/csky/Kconfig#L183
        // - https://github.com/torvalds/linux/blob/3a7e02c040b130b5545e4b115aada7bacd80a2b6/arch/alpha/include/asm/cache.h#L11
        // - https://www.xmos.com/download/The-XMOS-XS3-Architecture.pdf
        else => 64,
    };
}