linux-kernel - Re: [PATCH] pstore/ram : Add support for cached pages

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Date:   Wed, 10 Feb 2021 11:40:44 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Mukesh Ojha <mojha@...eaurora.org>, linux-kernel@...r.kernel.org
Cc:     tony.luck@...el.com, ccross@...roid.com, anton@...msg.org,
        keescook@...omium.org, Huang Yiwei <hyiwei@...eaurora.org>
Subject: Re: [PATCH] pstore/ram : Add support for cached pages

Hi--

On 2/10/21 6:52 AM, Mukesh Ojha wrote:
> There could be a sceanario where we define some region

                   scenario

> in normal memory and use them store to logs which is later
> retrieved by bootloader during warm reset.
> 
> In this scenario, we wanted to treat this memory as normal
> cacheable memory instead of default behaviour which
> is an overhead. Making it cacheable could improve
> performance.
> 
> This commit gives control to change mem_type from Device
> tree, and also documents the value for normal memory.
> 
> Signed-off-by: Huang Yiwei <hyiwei@...eaurora.org>
> Signed-off-by: Mukesh Ojha <mojha@...eaurora.org>
> ---
>  Documentation/admin-guide/ramoops.rst |  4 +++-
>  fs/pstore/ram.c                       |  1 +
>  fs/pstore/ram_core.c                  | 10 ++++++++--
>  3 files changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/admin-guide/ramoops.rst b/Documentation/admin-guide/ramoops.rst
> index b0a1ae7..8f107d8 100644
> --- a/Documentation/admin-guide/ramoops.rst
> +++ b/Documentation/admin-guide/ramoops.rst
> @@ -3,7 +3,7 @@ Ramoops oops/panic logger
>  
>  Sergiu Iordache <sergiu@...omium.org>
>  
> -Updated: 17 November 2011
> +Updated: 10 Feb 2021
>  
>  Introduction
>  ------------
> @@ -30,6 +30,8 @@ mapping to pgprot_writecombine. Setting ``mem_type=1`` attempts to use
>  depends on atomic operations. At least on ARM, pgprot_noncached causes the
>  memory to be mapped strongly ordered, and atomic operations on strongly ordered
>  memory are implementation defined, and won't work on many ARMs such as omaps.
> +Setting ``mem_type=2`` attempts to treat the memory region as normal memory,

Does "mem_type=" work?  or does it need to be "mem-type=", as below?
I.e., do both of them work?


> +which enables full cache on it. This can improve the performance.
>  
>  The memory area is divided into ``record_size`` chunks (also rounded down to
>  power of two) and each kmesg dump writes a ``record_size`` chunk of
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index ca6d8a8..b262c57 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -666,6 +666,7 @@ static int ramoops_parse_dt(struct platform_device *pdev,
>  		field = value;						\
>  	}
>  
> +	parse_u32("mem-type", pdata->record_size, pdata->mem_type);

              here^^^^^^^^^^


thanks.
-- 
~Randy