linux-kernel - Re: [PATCH] nubus: Avoid scanning "private" card resources

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Message-ID: <9b0d643e-2555-8d09-a47c-19196add3345@linux-m68k.org>
Date:   Wed, 22 Mar 2023 17:52:34 +1100 (AEDT)
From:   Finn Thain <fthain@...ux-m68k.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
cc:     linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nubus: Avoid scanning "private" card resources


On Wed, 22 Mar 2023, Finn Thain wrote:

> Some Nubus cards have many ROM resources. A single Radius video card
> produced well over a thousand entries under /proc/bus/nubus. Populating
> /proc/bus/nubus on a slow machine with several such cards installed takes
> long enough that the user may think that the system is wedged. All those
> procfs entries also consume significant RAM though they are not normally
> needed except by developers. Omit the "private" resources from
> /proc/bus/nubus/ by default and add a kernel parameter to enable them
> when needed. On the test machine, this saved 196 KiB and 5 seconds.
> 

This patch is nice and short but I suspect it can be improved upon. If the 
procfs entries are only needed for debugging then I should probably omit 
all of them by default, and save even more time and RAM. So I think I'll 
revise this patch.

> Tested-by: Stan Johnson <userm57@...oo.com>
> Signed-off-by: Finn Thain <fthain@...ux-m68k.org>
> ---
>  drivers/nubus/nubus.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nubus/nubus.c b/drivers/nubus/nubus.c
> index f70ba58dbc55..777099b8e818 100644
> --- a/drivers/nubus/nubus.c
> +++ b/drivers/nubus/nubus.c
> @@ -34,6 +34,9 @@
>  
>  LIST_HEAD(nubus_func_rsrcs);
>  
> +bool all_func_rsrcs;
> +module_param(all_func_rsrcs, bool, 0444);
> +
>  /* Meaning of "bytelanes":
>  
>     The card ROM may appear on any or all bytes of each long word in
> @@ -572,9 +575,9 @@ nubus_get_functional_resource(struct nubus_board *board, int slot,
>  			nubus_proc_add_rsrc(dir.procdir, &ent);
>  			break;
>  		default:
> -			/* Local/Private resources have their own
> -			   function */
> -			nubus_get_private_resource(fres, dir.procdir, &ent);
> +			if (all_func_rsrcs)
> +				nubus_get_private_resource(fres, dir.procdir,
> +							   &ent);
>  		}
>  	}
>  
>