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...
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Latest Posts
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
How Linux CFS Works: vruntime, Red-Black Trees, and Why Fairness Is Approximate
A CPU core runs one thread at a time. Everything else that looks concurrent is a lie the operating system maintains by switching. The policy...
Sarthak Bystander
22 Sept, 2026
How eBPF Works: Verifier, Maps, JIT, and Why the Kernel Runs Your Code
A kernel module can do almost anything. That is why loading one is a privileged act and why a bug in one can take the machine with it. eBPF ...
Sarthak Bystander
21 Sept, 2026
How TLS 1.3 Works: Certificates, 1-RTT Handshakes, and Why 0-RTT Is Replayable
TCP can carry bytes in order. It cannot tell you who is on the other end, and it cannot stop a path observer from reading those bytes. HTTPS...
Sarthak Bystander
20 Sept, 2026
How io_uring Works: Submission Queues, Completion Queues, and Why Batching Beats Syscalls
A tight loop of read and write pays for a privilege crossing on every operation. After Spectre-era mitigations that crossing got more expe...
Sarthak Bystander
19 Sept, 2026
How CPU Caches Work: Lines, Associativity, and False Sharing
A load that misses DRAM can cost hundreds of cycles. A load that hits L1 often costs a handful. That gap is why two programs with the same b...
Sarthak Bystander
18 Sept, 2026