Linux 3.15 Kernel Starts 10 Times Faster

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New patch could end user complaints about slow return from suspend.

Intel engineer Todd Brandt has apparently found a way by which a Linux system wakes up 10 times faster after a suspend-to-disk without playing with the power management infrastructure in the kernel. Kernel 3.15 has already included the patch.
His solution, which he describes in his project blog, is to optimize the driver for the ATA drives. The problem with the Resume function is that the ATA drivers wait until the ATA hardware is online. During this time, the kernel isn't doing anything but waiting for the hardware.
The new patch changes the ATA port driver to perform the wakeup command and then return immediately. The rest of the system can continue to operate without waiting for the ATA hardware. Brandt includes a similar patch for the SCSI subsystem.
These patches lead to a short period in which the system seems to have woken up from a deep sleep, but the disks are not yet available. Usually the user will not notice it, unless the suspend point happens to occur when the system is preparing to access the hard disk, in which case, the process would be similar to a wakeup without the patch.

04/15/2014

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