fio: add serialize_overlap option

[fio.git] / fio.1

diff --git a/fio.1 b/fio.1
index a3fba650f1c42d988ea5d1c9d5e8042e9d5e03b5..14359e609a961eab7a1bce506bdd01a2cc5a67aa 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -1044,6 +1044,20 @@ we simply do polling.
 Low watermark indicating when to start filling the queue again.  Default:
 \fBiodepth\fR.
 .TP
+.BI serialize_overlap \fR=\fPbool
+Serialize in-flight I/Os that might otherwise cause or suffer from data races.
+When two or more I/Os are submitted simultaneously, there is no guarantee that
+the I/Os will be processed or completed in the submitted order. Further, if
+two or more of those I/Os are writes, any overlapping region between them can
+become indeterminate/undefined on certain storage. These issues can cause
+verification to fail erratically when at least one of the racing I/Os is
+changing data and the overlapping region has a non-zero size. Setting
+\fBserialize_overlap\fR tells fio to avoid provoking this behavior by explicitly
+serializing in-flight I/Os that have a non-zero overlap. Note that setting
+this option can reduce both performance and the \fBiodepth\fR achieved.
+Additionally this option does not work when \fBio_submit_mode\fR is set to
+offload. Default: false.
+.TP
 .BI io_submit_mode \fR=\fPstr
 This option controls how fio submits the IO to the IO engine. The default is
 \fBinline\fR, which means that the fio job threads submit and reap IO directly.