HOWTO: add sg 'hipri' option

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/HOWTO b/HOWTO
index 372f268f55853efd7d6c10507e5f34e75d97cdf3..3ec86aff134732ef941d78f6ba69ae2154a29f38 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -2359,6 +2359,18 @@ with the caveat that when used on the command line, they must come after the
                transferred to the device. The writefua option is ignored with this
                selection.
 
+.. option:: hipri : [sg]
+
+       If this option is set, fio will attempt to use polled IO completions.
+       This will have a similar effect as (io_uring)hipri. Only SCSI READ and
+       WRITE commands will have the SGV4_FLAG_HIPRI set (not UNMAP (trim) nor
+       VERIFY). Older versions of the Linux sg driver that do not support
+       hipri will simply ignore this flag and do normal IO. The Linux SCSI
+       Low Level Driver (LLD) that "owns" the device also needs to support
+       hipri (also known as iopoll and mq_poll). The MegaRAID driver is an
+       example of a SCSI LLD. Default: clear (0) which does normal
+       (interrupted based) IO.
+
 .. option:: http_host=str : [http]
 
        Hostname to connect to. For S3, this could be the bucket hostname.