Re: [PATCH v3 3/4] xen/console: add build-time rate-limiting controls

Teddy Astie <[email protected]> Thu, 16 Jul 2026 11:59:34 +0200

Newsgroups	org.xenproject.lists.xen-devel
Message-ID	<1784195975.8631fc262581453bbf619ec5b2062170.19f6a5e0923000edb5@vates.tech>

Le 15/07/2026 à 22:24, [email protected] a écrit :
> From: Denis Mukhin <[email protected]>
> 
> Introduce CONFIG_PRINTK_RATELIMIT_MS and CONFIG_PRINTK_RATELIMIT_BURST
> for configuring rate-limiting policy at the compile time.
> 
> Use symbols for global rate-limiting initialization in the console driver.
> 
> Signed-off-by: Denis Mukhin <[email protected]>
> ---
> Changes since v2:
> - moved rate-limiting controls to common/Kconfig
> ---
>   xen/common/Kconfig         | 29 +++++++++++++++++++++++++++++
>   xen/drivers/char/console.c |  6 ++++--
>   2 files changed, 33 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> index da80fdba8469..fd22806884e0 100644
> --- a/xen/common/Kconfig
> +++ b/xen/common/Kconfig
> @@ -672,4 +672,33 @@ config PM_STATS
>   	  Enable collection of performance management statistics to aid in
>   	  analyzing and tuning power/performance characteristics of the system
>   
> +menu "Console rate-limiting"
> +
> +config PRINTK_RATELIMIT_MS
> +	int "printk rate-limiting time window (milliseconds)"
> +	default 5000
> +	help
> +	  Specifies the time window, in milliseconds, for rate-limited printk
> +	  messages. No more than `CONFIG_PRINTK_RATELIMIT_BURST` messages will be
> +	  printed within this window.
> +
> +	  Setting this value to 0 disables rate-limiting entirely.
> +
> +	  Rate-limited messages are those controlled by the `loglvl` and
> +	  `guest_loglvl` command-line parameters.
> +
> +config PRINTK_RATELIMIT_BURST
> +	int "printk rate-limited message burst size"
> +	default 10
> +	help
> +	  Defines the maximum number of rate-limited printk messages that may be
> +	  printed within each `CONFIG_PRINTK_RATELIMIT_MS` time window.
> +
> +	  Setting this value to 0 disables rate-limiting entirely.
> +
> +	  Rate-limited messages are those controlled by the `loglvl` and
> +	  `guest_loglvl` command-line parameters.
> +
> +endmenu
> +
>   endmenu

Given that setting 0 to either will disable rate limiting, would it be 
preferable instead to have a more general PRINTK_RATELIMIT toggle, where :

Setting it to true would enable configuration of ms and burst (rejecting 
0 if possible).
Setting it to false would set both to 0 hence disabling rate limiting by 
default.

And we do something like

static const unsigned int printk_ratelimit_ms =
   IS_ENABLED(CONFIG_PRINTK_RATELIMIT) ? CONFIG_PRINTK_RATELIMIT_MS : 0;

(similarly for burst)

?

Teddy

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