How DMA and the IOMMU Work: Addresses, Translation, and Why Devices Cannot Touch Arbitrary Host Memory
A network interface that just received a frame does not interrupt the CPU so the processor can copy the payload. The device writes the frame...
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How BGP Works: AS Paths, Path Attributes, and Why the Internet Is Not Shortest-Path
A packet from a laptop in Mumbai to a server in Frankfurt does not ask the Internet for the shortest path. It follows a route that some netw...
Sarthak Bystander
9 Oct, 2026
How Memory Ordering Works: Store Buffers, Barriers, and Why x86 Is Not Sequentially Consistent
Two threads can each write a flag and then read the other thread's flag, and both reads can return the old value. Nothing in the source ...
Sarthak Bystander
8 Oct, 2026
How UTF-8 and Unicode Work: Code Points, Bytes, and Why Length Is Three Numbers
A string that looks like one character can be one byte, two bytes, or several code points that a font draws as a single glyph. len in one l...
Sarthak Bystander
7 Oct, 2026
How IEEE 754 Floating Point Works: Formats, Rounding, and Why 0.1 Is Not Exact
A statement like 0.1 + 0.2 == 0.3 fails in Python, JavaScript, Java, Go, and C for the same reason. None of those languages stored the deci...
Sarthak Bystander
6 Oct, 2026
How Linux Interrupts Work: Hardware IRQs, Softirqs, and Why Threaded Handlers Exist
A NIC that just received a frame cannot wait for the current process to finish a syscall. The device raises a hardware interrupt. The CPU st...
Sarthak Bystander
29 Sept, 2026
How Linux Signals Work: Pending Masks, Delivery on Return to Userspace, and Why They Are Not Interrupts
A process that spends all its time in a tight userspace loop never notices SIGTERM until the kernel has a chance to put that process back on...
Sarthak Bystander
28 Sept, 2026
How Futexes Work: Userspace Fast Path, Wait Queues, and Why Mutexes Avoid Syscalls
A mutex that takes a system call on every lock and unlock would dominate a hot critical section. The uncontended case is a few atomic instru...
Sarthak Bystander
25 Sept, 2026
How epoll Works: Readiness, Level vs Edge Trigger, and Why select Doesn't Scale
A process that accepts ten thousand TCP connections cannot afford to ask the kernel about each socket in turn. select(2) and poll(2) copy ...
Sarthak Bystander
24 Sept, 2026
How RCU Works: Grace Periods, Quiescent States, and Why Readers Skip Locks
A shared linked list in the kernel can be walked by thousands of cores at once. A writer still has to insert or delete a node. If every walk...
Sarthak Bystander
23 Sept, 2026