// BLOG · PAGE 6 OF 8
ALL POSTS · PAGE 6 / 8
Reorder three fields and a struct shrinks from 24 bytes to 16 — a 33% memory cut with zero code changes. Where padding comes from, how to see it with pahole, and when packing is a trap.
UB doesn't mean 'returns garbage' — it means the optimizer may assume it never happens and reason backwards from that. How signed overflow checks get deleted, why time-travel is real, and the sanitizer workflow that catches it.
Flash can't overwrite in place, erases in giant blocks, and wears out per cell — so every SSD runs a translation layer that remaps, garbage-collects, and levels wear behind your back. Write amplification, TRIM, and the cliff at 90% full, explained.
Signed integers could have been encoded a dozen ways. Hardware settled on two's complement because it makes the adder ignorant of sign — one circuit for everything. The same choice explains INT_MIN, sign extension bugs, and why abs() can return a negative number.
Between pressing enter and your first line of code, the kernel parses an ELF file, maps segments, loads an interpreter you didn't know existed, and that interpreter relocates half your program. A tour of the machinery under ./a.out.
One lock burns CPU while it waits; the other pays a syscall to sleep. The right choice depends on hold time versus context-switch cost — and the best answer, futexes and adaptive locks, is 'both, in that order'.
A 'simple' name lookup traverses your language runtime, nsswitch, a stub resolver, a recursive resolver, and up to three tiers of authoritative servers — with caches at every layer that disagree. Map the path once and DNS bugs become findable.
A 'load balancer' is anywhere from a NAT rewrite to a full HTTP proxy with retry logic — and the algorithm matters less than people think while the health checking matters more. The mechanics, from ECMP and Maglev down to power-of-two-choices.
Every queue advertises delivery guarantees; every distributed-systems engineer eventually learns the ack-crash window makes duplicates inevitable. Why exactly-once is really exactly-once *processing*, and the idempotency patterns that make it true.
RAID levels are three ideas — stripe, mirror, parity — composed. The interesting parts are the failure math: why RAID 5 rebuilds fail at modern disk sizes, what the write hole is, and why RAID is not backup, mathematically.
Every exploit needs an address; ASLR's bet is that the attacker shouldn't know any. How Linux randomizes stack, heap, and libraries, why PIE took years to become default, and the leak-one-pointer reality that keeps ASLR a speed bump, not a wall.
The same loop over the same data runs 5x faster when the array is sorted. The instructions are identical. The difference is a gambler inside your CPU that's either winning or losing.