How the Linux VFS Works: Inodes, Dentries, and Why Paths Are Not Files
An open("/var/log/app.log", O_RDONLY) does not hand the kernel a file. It hands the kernel a string. The Virtual File System (VFS...
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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 the Linux Page Cache Works: Radix Trees, Writeback, and Why read() Hits DRAM
A process asks for a few bytes from a file. The kernel may return them without asking the storage device for anything at all—not because the...
Sarthak Bystander
27 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
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