https://nalar.dev/tags/eventfd/ Recent content in Eventfd on Nalar Hugo en-us Fri, 18 Sep 2026 00:00:00 +0000 https://nalar.dev/eventfd-aggregates-notifications-in-a-kernel-counter/ Fri, 18 Sep 2026 00:00:00 +0000 https://nalar.dev/eventfd-aggregates-notifications-in-a-kernel-counter/ <p>An <code>eventfd</code> can absorb several notification writes before userspace services the descriptor. The kernel stores those writes in a 64-bit counter, so readiness represents pending counter state rather than a queue containing one record per notification.</p> <p>That distinction matters in event loops. A producer can add values while a consumer is occupied, and the next read can collapse accumulated state into one result. With <code>EFD_SEMAPHORE</code>, the same object exposes a different consumption rule without changing its readiness model.</p>