Add ability to invoke fallocate() FALLOC_FL_KEEP_SIZE.
Linux offers fallocate() and the FALLOC_FL_KEEP_SIZE option as
an alternative to posix_fallocate(). When FALLOC_FL_KEEP_SIZE is
specified for an falloc request going beyond the end of the file,
the requested blocks get preallocated without changing the apparent
size of the file. This is is a commonly recommended use of fallocate()
for workloads performing append writes.
This patch modifies the fallocate option from a boolean option
to a string option accepting none/posix/keep/0/1. 'keep' is only
made available on systems where FALLOC_FL_KEEP_SIZE is available
(i.e., Linux at this time). If specified, fallocate() is used
with FALLOC_FL_KEEP_SIZE set. 'none' disables pre-allocation while
'posix' uses posix_fallocate(). The default behavior remains unchaned,
i.e., invoking posix_fallocate. The settings '0'/'1' are there to
provide backward compatibility for users who had explicitly set the
boolean option.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/fio.1 b/fio.1
index 0ced604..ad5040b 100644
--- a/fio.1
+++ b/fio.1
@@ -220,10 +220,32 @@
Default is to use the internal generator, which is often of better quality and
faster. Default: false.
.TP
-.BI fallocate \fR=\fPbool
-By default, fio will use fallocate() to advise the system of the size of the
-file we are going to write. This can be turned off with fallocate=0. May not
-be available on all supported platforms.
+.BI fallocate \fR=\fPstr
+Whether pre-allocation is performed when laying down files. Accepted values
+are:
+.RS
+.RS
+.TP
+.B none
+Do not pre-allocate space.
+.TP
+.B posix
+Pre-allocate via posix_fallocate().
+.TP
+.B keep
+Pre-allocate via fallocate() with FALLOC_FL_KEEP_SIZE set.
+.TP
+.B 0
+Backward-compatible alias for 'none'.
+.TP
+.B 1
+Backward-compatible alias for 'posix'.
+.RE
+.P
+May not be available on all supported platforms. 'keep' is only
+available on Linux. If using ZFS on Solaris this must be set to 'none'
+because ZFS doesn't support it. Default: 'posix'.
+.RE
.TP
.BI fadvise_hint \fR=\fPbool
Disable use of \fIposix_fadvise\fR\|(2) to advise the kernel what I/O patterns