POSIX_FADVISE_NOREUSE is now supported in Linux[1]. Updates text regarding former no op behavior. Indicates the readahead policy and treatment of file pages read with this flag. [1]: https://lore.kernel.org/linux-mm/20221230215252.2628425-2-yuzhao@xxxxxxxxxx/ Signed-off-by: T.J. Alumbaugh <talumbau@xxxxxxxxxx> --- man2/posix_fadvise.2 | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/man2/posix_fadvise.2 b/man2/posix_fadvise.2 index 57c65c810..5eba3988b 100644 --- a/man2/posix_fadvise.2 +++ b/man2/posix_fadvise.2 @@ -64,7 +64,10 @@ The specified data will be accessed only once. .IP Before Linux 2.6.18, \fBPOSIX_FADV_NOREUSE\fP had the same semantics as \fBPOSIX_FADV_WILLNEED\fP. -This was probably a bug; since Linux 2.6.18, this flag is a no-op. +This was probably a bug; from Linux 2.6.18 until Linux 6.2 this flag was +a no-op. From Linux 6.3 and beyond, \fBPOSIX_FADV_NOREUSE\fP signals +that that the LRU algorithm can ignore access to mapped page cache marked +by this flag. This is useful, for example, while streaming large files. .TP .B POSIX_FADV_WILLNEED The specified data will be accessed in the near future. @@ -151,11 +154,12 @@ to .I off_t in POSIX.1-2001 TC1. .SH NOTES -Under Linux, \fBPOSIX_FADV_NORMAL\fP sets the readahead window to the -default size for the backing device; \fBPOSIX_FADV_SEQUENTIAL\fP doubles -this size, and \fBPOSIX_FADV_RANDOM\fP disables file readahead entirely. -These changes affect the entire file, not just the specified region -(but other open file handles to the same file are unaffected). +Under Linux, \fBPOSIX_FADV_NORMAL\fP and \fBPOSIX_FADV_NOREUSE\fP +set the readahead window to the default size for the backing device; +\fBPOSIX_FADV_SEQUENTIAL\fP doubles this size, and +\fBPOSIX_FADV_RANDOM\fP disables file readahead entirely. These changes +affect the entire file, not just the specified region (but other open +file handles to the same file are unaffected). .PP The contents of the kernel buffer cache can be cleared via the .I /proc/sys/vm/drop_caches -- 2.40.0.rc1.284.g88254d51c5-goog
