On Fri, Jun 22 2007, Kristen Carlson Accardi wrote: > On Thu, 21 Jun 2007 15:08:32 +0200 > Jens Axboe <jens.axboe@xxxxxxxxxx> wrote: > > > On Wed, Jun 20 2007, Kristen Carlson Accardi wrote: > > > Enable Aggressive Link Power management for AHCI controllers. > > > > > > This patch will set the correct bits to turn on Aggressive > > > Link Power Management (ALPM) for the ahci driver. This > > > will cause the controller and disk to negotiate a lower > > > power state for the link when there is no activity (see > > > the AHCI 1.x spec for details). This feature is mutually > > > exclusive with Hot Plug, so when ALPM is enabled, Hot Plug > > > is disabled. ALPM will be enabled by default, but it is > > > settable via the scsi host syfs interface. Possible > > > settings for this feature are: > > > > > > Setting Effect > > > ---------------------------------------------------------- > > > min_power ALPM is enabled, and link set to enter > > > lowest power state (SLUMBER) when idle > > > Hot plug not allowed. > > > > > > max_performance ALPM is disabled, Hot Plug is allowed > > > > > > medium_power ALPM is enabled, and link set to enter > > > second lowest power state (PARTIAL) when > > > idle. Hot plug not allowed. > > > > > > Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@xxxxxxxxx> > > > > A suggestion (it comes with a patch!) - default to max_power/almp off, > > not min_power. For two reasons: > > > > - There's such a big performance difference between the two, you really > > want max_power when booting. > > > > - It's a lot better to default to no change, than default to enabling > > something new. > > Sounds reasonable to me. Distros/users can decide if they want to have > scripts that enable this after boot to run at min_power. Exactly, it needs to be handled by some power management daemon anyway and be integrated with power savings in general. You could use io load to determine when to enable/disable alpm, for instance. > Acked-by: Kristen Carlson Accardi <kristen.c.accardi@xxxxxxxxx> Will you integrate it into the next posting? -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
