https://www.scrivano.org/tags/mount/ Recent content in Mount on *scratch* Hugo en Sat, 06 Jun 2026 10:03:54 +0000 https://www.scrivano.org/2019/12/27/avoid-a-memory-page-allocation-on-mount/ Fri, 27 Dec 2019 16:16:33 +0000 https://www.scrivano.org/2019/12/27/avoid-a-memory-page-allocation-on-mount/ <p>While working on crun, I got surprised by how much time the kernel spent in the <code>copy_mount_options</code> function. A container runtime issues a large number of <code>mount(2)</code> syscalls during startup — bind mounts, proc, sysfs, devtmpfs, and more — many of them with no extra options to pass. It turned out that passing an empty string instead of <code>NULL</code> for the data argument caused the kernel to allocate a full memory page and attempt a copy from user space on every one of those calls, adding measurable overhead.</p>