Re: [PATCH] ACPI: Add debugfs support for ACPICA boot time measurement.

[Len Brown <lenb@kernel.org>]

On 11/07/2012 08:49 PM, Lv Zheng wrote:
> ACPICA defines the following initialization steps that must be called to
> make ACPICA functional:
>   1. acpi_initialize_tables
>   2. acpi_initialize_subsystem
>   3. acpi_load_tables
>   4. acpi_enable_subsystem
>   5. acpi_initialize_objects
>   6. OSPM specific bus scanning
>   7. acpi_update_all_gpes
> This patch allows developers to check the execution time of such bootup
> steps through /sys/kernel/debug/acpi/acpica_init_time.
> 
> The ACPICA 20121018 release measurement result is as follows:
> ========================================
>     0.000000 acpi_initialize_tables
>     0.000034 acpi_initialize_subsystem
>     0.004822 acpi_load_tables
>     0.003351 acpi_enable_subsystem
>     0.003204 acpi_initialize_objects
>     0.045082 acpi_bus_scan
>     0.000023 acpi_bus_scan_fixed
>     0.000017 acpi_update_all_gpes
> ========================================
> The left column is the execution time in timeval (sec.usec) format.
> The right column indicates the name of the initialization step.

As you've identified that 80% of the ACPI startup time goes to acpi_bus_scan(),
have you identified any ways to make acpi_bus_scan() faster?

Do these numbers vary greatly when run on different machines?

thanks,
-Len Brown, Intel Open Source Technology Center