Re: git: 40b287054521 - main - mi_startup: Instrument the bubblesort with TSLOG

On 5/19/23 15:49, Colin Percival wrote:
> The branch main has been updated by cperciva:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=40b287054521f0a92e5ae9a26e6a87d17ee85eea
> 
> commit 40b287054521f0a92e5ae9a26e6a87d17ee85eea
> Author:     Colin Percival <cperciva@FreeBSD.org>
> AuthorDate: 2023-05-19 13:46:42 +0000
> Commit:     Colin Percival <cperciva@FreeBSD.org>
> CommitDate: 2023-05-19 13:46:42 +0000
> 
>      mi_startup: Instrument the bubblesort with TSLOG
>      
>      The bubblesort of SYSINITs is currently responsible for 7% of the
>      kernel boot time when booting a 1 CPU / 128 MB VM under Firecracker.
>      
>      It needs to be replaced with a faster sort, but until that happens
>      at least instrumenting it with TSLOG makes it show up in flamecharts.
> ---
>   sys/kern/init_main.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
> index 1974c4e68ce4..e4cb501bc57b 100644
> --- a/sys/kern/init_main.c
> +++ b/sys/kern/init_main.c
> @@ -255,6 +255,7 @@ restart:
>   	 * Perform a bubble sort of the system initialization objects by
>   	 * their subsystem (primary key) and order (secondary key).
>   	 */
> +	TSENTER2("bubblesort");
>   	for (sipp = sysinit; sipp < sysinit_end; sipp++) {
>   		for (xipp = sipp + 1; xipp < sysinit_end; xipp++) {
>   			if ((*sipp)->subsystem < (*xipp)->subsystem ||
> @@ -266,6 +267,7 @@ restart:
>   			*xipp = save;
>   		}
>   	}
> +	TSEXIT2("bubblesort");
>   
>   	last = SI_SUB_COPYRIGHT;
>   #if defined(VERBOSE_SYSINIT)
> 

Hi Colin,

If all kernel modules and the kernel could sort their SYSINIT() and 
SYSUNINIT() data at compile time, then all you need to do, is to merge 
two sorted lists, when loading new modules.

Maybe this even could be part of the compiler's existing __constructor 
attribute. In FreeBSD we have an example of build boot loader modules, 
and statically sorting all sysinit data at compile time. See the tool I 
made many years ago for this purpose:

stand/usb/tools/sysinit.c

What do you think?

--HPS