Madvise

Linux 23 Sep 2026 3 min read

MADV_WIPEONFORK Replaces Inherited Private Memory with Zeroes

MADV_WIPEONFORK Replaces Inherited Private Memory with Zeroes A normal fork() gives the child mappings derived from the parent’s address space, with private writable pages commonly handled through copy-on-write. MADV_WIPEONFORK changes that inheritance rule for a selected private anonymous range: the mapping remains present in the child, but its contents are zero-filled there. The parent keeps its existing bytes. The operation therefore changes child-visible memory at the process-creation boundary rather than erasing the parent’s range.

Linux madvise

Linux 23 Sep 2026 4 min read

MADV_DONTFORK Excludes Memory Ranges from Child Address Spaces

MADV_DONTFORK changes a specific part of Linux process creation: a mapping marked with this advice is not made available in the child created by fork(). The parent keeps the mapping. The child starts without that address range, so an address that was valid there in the parent is not automatically valid in the child. This is a semantic control over mapping inheritance, not a cache hint. It belongs to the Linux-specific madvise() operations whose effects can change memory behavior.

Linux Virtual Memory

Linux 19 Sep 2026 4 min read

MADV_FREE Marks Anonymous Pages for Lazy Reclaim

MADV_FREE does not immediately replace a private anonymous page with zeros. It marks eligible pages as disposable, allowing Linux to reclaim them later. Until reclaim actually occurs, existing bytes can remain observable. A write before reclaim cancels the disposable state for the affected page. That timing makes MADV_FREE distinct from advice that immediately changes the process-visible state of a range. It is a lazy reclamation contract: the application declares that old contents are expendable, while the kernel chooses when physical memory is recovered.

Linux Memory