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Diffstat (limited to 'share/man/man4/ahci.4')
| -rw-r--r-- | share/man/man4/ahci.4 | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/share/man/man4/ahci.4 b/share/man/man4/ahci.4 index 0173e1e7bc00..46660d3a2739 100644 --- a/share/man/man4/ahci.4 +++ b/share/man/man4/ahci.4 @@ -25,7 +25,7 @@ .\" .\" $FreeBSD$ .\" -.Dd June 26, 2009 +.Dd August 24, 2009 .Dt AHCI 4 .Os .Sh NAME @@ -60,6 +60,13 @@ single MSI vector used, if supported (default); .It 2 multiple MSI vectors used, if supported; .El +.It Va hint.ahci.X.ccc +controls Command Completion Coalescing (CCC) usage by the specified controller. +Non-zero value enables CCC and defines maximum time (in ms), request can wait +for interrupt, if there are some more requests present on controller queue. +CCC reduces number of context switches on systems with many parallel requests, +but it can decrease disk performance on some workloads due to additional +command latency. .It Va hint.ahcich.X.pm_level controls SATA interface Power Management for specified channel, allowing some power to be saved at the cost of additional command @@ -74,7 +81,15 @@ device is allowed to initiate PM state change, host is passive; host initiates PARTIAL PM state transition every time port becomes idle; .It 3 host initiates SLUMBER PM state transition every time port becomes idle. +.It 4 +driver initiates PARTIAL PM state transition 1ms after port becomes idle; +.It 5 +driver initiates SLUMBER PM state transition 125ms after port becomes idle. .El +Some controllers, such as ICH8, do not implement modes 2 and 3 with NCQ used. +Because of artificial entering latency, performance degradation in modes +4 and 5 is much smaller then in modes 2 and 3. +.Pp Note that interface Power Management is not compatible with device presence detection. You will have to reset bus manually on device hot-plug. |