linux-kernel - Re: [PATCH] RAS/CEC: Reduce offline page threshold for Intel systems

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Date:   Tue, 2 Aug 2022 12:07:26 +0000
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Tony Luck <tony.luck@...el.com>
Cc:     bp@...en8.de, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev, x86@...nel.org
Subject: Re: [PATCH] RAS/CEC: Reduce offline page threshold for Intel systems

On Fri, Jul 01, 2022 at 12:12:39PM -0700, Tony Luck wrote:
> A large scale study of memory errors on Intel systems in data centers
> showed that aggressively taking pages with corrected errors offline is
> the best strategy of using corrected errors as a predictor of future
> uncorrected errors.
> 
> It is unknown whether this would help other vendors. There are some
> indicators that it would not.
> 
> Set the threshold to "2" on Intel systems.
> 
> Do-not-apply-without-agreement-from-AMD
> Signed-off-by: Tony Luck <tony.luck@...el.com>

Hi Tony,
The guidance from our hardware folks is that this isn't necessary for our
systems. So I think restricting this to Intel systems is okay.

> ---
>  drivers/ras/cec.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
> index 42f2fc0bc8a9..b1fc193b2036 100644
> --- a/drivers/ras/cec.c
> +++ b/drivers/ras/cec.c
> @@ -556,6 +556,14 @@ static int __init cec_init(void)
>  	if (ce_arr.disabled)
>  		return -ENODEV;
>  
> +	/*
> +	 * Intel systems may avoid uncorreectable errors
> +	 * if pages with corrected errors are aggresively
> +	 * taken offline.
> +	 */

s/uncorreectable/uncorrectable/
s/aggresively/aggressively/

> +	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
> +		action_threshold = 2;
> +
>  	ce_arr.array = (void *)get_zeroed_page(GFP_KERNEL);
>  	if (!ce_arr.array) {
>  		pr_err("Error allocating CE array page!\n");
> --

Looks good to me overall.

Reviewed-by: Yazen Ghannam <yazen.ghannam@....com>

Thanks,
Yazen