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[PR 195033] Document mps.enable_ssu

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mps(4) sends StartStopUnit to SATA direct-access devices during shutdown.
Document the tunables which control that behavior.

PR:		195033
Reviewed by:	scottl
Approved by:	jhb
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D4456
This commit is contained in:
rpokala 2015-12-11 21:50:59 +00:00
parent 662efc558a
commit 7fd0d14bf5
1 changed files with 37 additions and 2 deletions
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39
share/man/man4/mps.4
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@ -34,7 +34,7 @@
.\" $Id: //depot/SpectraBSD/head/share/man/man4/mps.4#6 $
.\" $FreeBSD$
.\"
.Dd January 3, 2013
.Dd December 9, 2015
.Dt MPS 4
.Os
.Sh NAME
@ -129,6 +129,8 @@ driver instance, set the following tunable value in
dev.mps.X.disable_msix=1
.Ed
.Pp
where X is the adapter number.
.Pp
To set the maximum number of DMA chains allocated for all adapters,
set the following variable in
.Xr loader.conf 5 :
@ -166,6 +168,39 @@ The maximum number of active I/O command seen since boot is shown in the
dev.mps.X.io_cmds_highwater
.Xr sysctl 8
variable.
.Pp
The adapter can issue the
.Sy StartStopUnit
SCSI command to SATA direct-access devices during shutdown, to allow the
device to quiesce before being powered down.
To control this feature for all adapters, set the
.Bd -literal -offset indent
hw.mps.enable_ssu
.Ed
.Pp
tunable value in
.Xr loader.conf 5
to one of the following values:
.Bl -tag -width 6n -offset indent
.It 0
Do not send SSU to either HDDs or SSDs.
.It 1
Send SSU to SSDs, but not to HDDs; this is the default value.
.It 2
Send SSU to HDDs, but not to SSDs.
.It 3
Send SSU to both HDDs and SSDs.
.El
.Pp
To control the feature for a specific adapter, set the following tunable
value in
.Xr loader.conf 5 :
.Bd -literal -offset indent
dev.mps.X.enable_ssu
.Ed
.Pp
where X is the adapter number.
The same set of values are valid as for all adapters.
.Sh DEBUGGING
To enable debugging prints from the
.Nm
@ -218,7 +253,7 @@ This man page was written by
This driver has a couple of known shortcomings:
.Bl -bullet -compact
.It
No userland utility available (e.g.
No userland utility available (e.g.,
.Xr mptutil 8 ) .
.It
The driver probes devices sequentially.