diff --git a/man2/statx.2 b/man2/statx.2 index 20f3ec031..4a4d30251 100644 --- a/man2/statx.2 +++ b/man2/statx.2 @@ -464,27 +464,33 @@ against a cryptographic hash that covers the entire file (e.g., via a Merkle tree). .TP .BR STATX_ATTR_DAX (since Linux 5.8) -The file is in the DAX (cpu direct access) state. DAX state attempts to +The file is in the DAX (cpu direct access) state. +DAX state attempts to minimize software cache effects for both I/O and memory mappings of this file. It requires a file system which has been configured to support DAX. .PP -DAX generally assumes all accesses are via cpu load / store instructions which -can minimize overhead for small accesses, but may adversely affect cpu -utilization for large transfers. +DAX generally assumes all accesses are via CPU load / store instructions +which can minimize overhead for small accesses, +but may adversely affect CPU utilization for large transfers. .PP File I/O is done directly to/from user-space buffers and memory mapped I/O may -be performed with direct memory mappings that bypass kernel page cache. +be performed with direct memory mappings that bypass the kernel page cache. .PP While the DAX property tends to result in data being transferred synchronously, -it does not give the same guarantees of O_SYNC where data and the necessary -metadata are transferred together. +it does not give the same guarantees as the +.B O_SYNC +flag (see +.BR open (2)), +where data and the necessary metadata are transferred together. .PP -A DAX file may support being mapped with the MAP_SYNC flag, which enables a +A DAX file may support being mapped with the +.B MAP_SYNC +flag, which enables a program to use CPU cache flush instructions to persist CPU store operations without an explicit -.BR fsync(2). +.BR fsync (2). See -.BR mmap(2) +.BR mmap (2) for more information. .SH RETURN VALUE On success, zero is returned.