Merge branch 'chunked-iolog-reading' of https://github.com/aclamk/fio

[fio.git] / fio.1

diff --git a/fio.1 b/fio.1
index c744d1add10f869284127b0261873404ebe2c098..4386f8577b8c6f8a63eb12b40d65b22d9b77d2c1 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -757,7 +757,7 @@ Sequential reads.
 Sequential writes.
 .TP
 .B trim
-Sequential trims (Linux block devices only).
+Sequential trims (Linux block devices and SCSI character devices only).
 .TP
 .B randread
 Random reads.
@@ -766,7 +766,7 @@ Random reads.
 Random writes.
 .TP
 .B randtrim
-Random trims (Linux block devices only).
+Random trims (Linux block devices and SCSI character devices only).
 .TP
 .B rw,readwrite
 Sequential mixed reads and writes.
@@ -1120,7 +1120,9 @@ at past I/O history. This means that some blocks may not be read or written,
 and that some blocks may be read/written more than once. If this option is
 used with \fBverify\fR and multiple blocksizes (via \fBbsrange\fR),
 only intact blocks are verified, i.e., partially\-overwritten blocks are
-ignored.
+ignored.  With an async I/O engine and an I/O depth > 1, it is possible for
+the same block to be overwritten, which can cause verification errors.  Either
+do not use norandommap in this case, or also use the lfsr random generator.
 .TP
 .BI softrandommap \fR=\fPbool
 See \fBnorandommap\fR. If fio runs with the random block map enabled and
@@ -1522,7 +1524,8 @@ SCSI generic sg v3 I/O. May either be synchronous using the SG_IO
 ioctl, or if the target is an sg character device we use
 \fBread\fR\|(2) and \fBwrite\fR\|(2) for asynchronous
 I/O. Requires \fBfilename\fR option to specify either block or
-character devices. The sg engine includes engine specific options.
+character devices. This engine supports trim operations. The
+sg engine includes engine specific options.
 .TP
 .B null
 Doesn't transfer any data, just pretends to. This is mainly used to
@@ -2054,6 +2057,11 @@ to replay a workload captured by blktrace. See
 replay, the file needs to be turned into a blkparse binary data file first
 (`blkparse <device> \-o /dev/null \-d file_for_fio.bin').
 .TP
+.BI read_iolog_chunked \fR=\fPbool
+Determines how iolog is read. If false (default) entire \fBread_iolog\fR will
+be read at once. If selected true, input from iolog will be read gradually.
+Useful when iolog is very large, or it is generated.
+.TP
 .BI replay_no_stall \fR=\fPbool
 When replaying I/O with \fBread_iolog\fR the default behavior is to
 attempt to respect the timestamps within the log and replay them with the
@@ -2370,6 +2378,11 @@ that the written data is also correctly read back. If the data direction
 given is a read or random read, fio will assume that it should verify a
 previously written file. If the data direction includes any form of write,
 the verify will be of the newly written data.
+.P
+To avoid false verification errors, do not use the norandommap option when
+verifying data with async I/O engines and I/O depths > 1.  Or use the
+norandommap and the lfsr random generator together to avoid writing to the
+same offset with muliple outstanding I/Os.
 .RE
 .TP
 .BI verify_offset \fR=\fPint