blktrace: fix bugs in accounting

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 3f258db8cf94178da849d75d4a8fb4c028e5367f..bcc72b5882be95e4804a641f151cde13b214b432 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -387,6 +387,8 @@ rw=str              Type of io pattern. Accepted values are:
                        randread        Random reads
                        rw,readwrite    Sequential mixed reads and writes
                        randrw          Random mixed reads and writes
+                       trimwrite       Mixed trims and writes. Blocks will be
+                                       trimmed first, then written to.
 
                For the mixed io types, the default is to split them 50/50.
                For certain types of io the result may still be skewed a bit,
@@ -770,6 +772,15 @@ ioengine=str       Defines how the job issues io to the file. The following
                                necessary environment variables to work with
                                hdfs/libhdfs properly.
 
+                       mtd     Read, write and erase an MTD character device
+                               (e.g., /dev/mtd0). Discards are treated as
+                               erases. Depending on the underlying device
+                               type, the I/O may have to go in a certain
+                               pattern, e.g., on NAND, writing sequentially
+                               to erase blocks and discarding before
+                               overwriting. The writetrim mode works well
+                               for this constraint.
+
                        external Prefix to specify loading an external
                                IO engine object file. Append the engine
                                filename, eg ioengine=external:/tmp/foo.o
@@ -809,6 +820,18 @@ iodepth_low=int    The low water mark indicating when to start filling
                after fio has filled the queue of 16 requests, it will let
                the depth drain down to 4 before starting to fill it again.
 
+io_submit_mode=str     This option controls how fio submits the IO to
+               the IO engine. The default is 'inline', which means that the
+               fio job threads submit and reap IO directly. If set to
+               'offload', the job threads will offload IO submission to a
+               dedicated pool of IO threads. This requires some coordination
+               and thus has a bit of extra overhead, especially for lower
+               queue depth IO where it can increase latencies. The benefit
+               is that fio can manage submission rates independently of
+               the device completion rates. This avoids skewed latency
+               reporting if IO gets back up on the device side (the
+               coordinated omission problem).
+
 direct=bool    If value is true, use non-buffered io. This is usually
                O_DIRECT. Note that ZFS on Solaris doesn't support direct io.
                On Windows the synchronous ioengines don't support direct io.
@@ -1468,6 +1491,11 @@ log_store_compressed=bool        If set, and log_compression is also set,
                command line parameter. The files will be stored with a
                .fz suffix.
 
+block_error_percentiles=bool   If set, record errors in trim block-sized
+               units from writes and trims and output a histogram of
+               how many trims it took to get to errors, and what kind
+               of error was encountered.
+
 lockmem=int    Pin down the specified amount of memory with mlock(2). Can
                potentially be used instead of removing memory or booting
                with less memory to simulate a smaller amount of memory.
@@ -1507,13 +1535,13 @@ clat_percentiles=bool Enable the reporting of percentiles of
                 completion latencies.
 
 percentile_list=float_list Overwrite the default list of percentiles
-               for completion latencies. Each number is a floating
-               number in the range (0,100], and the maximum length of
-               the list is 20. Use ':' to separate the numbers, and
-               list the numbers in ascending order. For example,
-               --percentile_list=99.5:99.9 will cause fio to report
-               the values of completion latency below which 99.5% and
-               99.9% of the observed latencies fell, respectively.
+               for completion latencies and the block error histogram.
+               Each number is a floating number in the range (0,100],
+               and the maximum length of the list is 20. Use ':'
+               to separate the numbers, and list the numbers in ascending
+               order. For example, --percentile_list=99.5:99.9 will cause
+               fio to report the values of completion latency below which
+               99.5% and 99.9% of the observed latencies fell, respectively.
 
 clocksource=str        Use the given clocksource as the base of timing. The
                supported options are:
@@ -1716,6 +1744,7 @@ be the starting port number since fio will use a range of ports.
                1         : allocate space immidietly inside defragment event,
                            and free right after event
 
+[mtd] skip_bad=bool    Skip operations against known bad blocks.
 
 
 6.0 Interpreting the output