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Industries · Systems and OS

For kernels, runtimes and toolchains

ByteAsk reads the struct layout from the binary, measures before it claims a speedup, and cites the x86-64 SDM by section.

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ByteAsk v0.1.12 · 01-false-sharingFind out why, and fix it.
🔧 cpp_layout · bench/shard_replay.cppSymbolStats: size 32  (source: pahole (exact))     0  messages  (8 B)     8  shares  (8 B)    16  notional  (8 B)    24  last_price_ticks  (4 B)    28  instrument_id  (4 B)0 of 32 bytes are padding (0%). No member straddles a 64B cacheline.🔧 cpp_perfMethod: plain timing (perf unavailable) (repeat=9, warmup=1 untimed)A: mean 0.1903s over 9 run(s) (±0.0016s stderr)B: mean 0.0795s over 9 run(s) (±0.0004s stderr)B is 2.39x faster than A (delta 0.1108s > noise gate 0.0041s; significant).-struct SymbolStats {+struct alignas(64) SymbolStats {

Recorded ByteAsk session on a four-shard benchmark: two instruments on one 64-byte cache line, fixed with one word and measured against a noise gate.

Standards it can cite

x86-64 SDM · ELF

x86_ref: x86-64 Software Developer Manual

search_docsx86 SDM cache line fill 64-byte aligned cache line MESI shared invalid snoop write by another processor
Intel 64 and IA-32 Architectures Software Developer's Manual§14.2 CACHING TERMINOLOGY · p.3618
When operating in an MP system, IA-32 processors (beginning with the Intel486 processor) and Intel 64 processors
have the ability to snoop other processor’s accesses to system memory and to their internal caches. They use this
snooping ability to keep their internal caches consistent both with system memory and with the caches in other
processors on the bus. For example, in the Pentium and P6 family processors, if through snooping one processor
detects that another processor intends to write to a memory location that it currently has cached in shared state,
the snooping processor will invalidate its cache line forcing it to perform a cache line fill the next time it accesses
the same memory location.
ref 325462-091-sdm-vol-1-2abcd-3abcd-4-v2-1:14.2:545:2 · captured 2026-10-26

The tools it runs for Systems and OS

  • perf
  • Callgrind
  • gdb
  • readelf
  • objdump
  • make
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