linux-kernel - Re: [PATCH] crash_core: export vmemmap when CONFIG_SPARSEMEM

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Message-ID: <ZWQEP4SczFh+GUHq@MiWiFi-R3L-srv>
Date:   Mon, 27 Nov 2023 10:51:43 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Huang Shijie <shijie@...amperecomputing.com>
Cc:     k-hagio-ab@....com, lijiang@...hat.com, akpm@...ux-foundation.org,
        vgoyal@...hat.com, dyoung@...hat.com, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, patches@...erecomputing.com
Subject: Re: [PATCH] crash_core: export vmemmap when CONFIG_SPARSEMEM_VMEMMAP
 is enabled

Hi,

On 11/27/23 at 10:07am, Huang Shijie wrote:
> In memory_model.h, if CONFIG_SPARSEMEM_VMEMMAP is configed,
> kernel will use vmemmap to do the __pfn_to_page/page_to_pfn,
> and kernel will not use the "classic sparse" to do the
> __pfn_to_page/page_to_pfn.
> 
> So export the vmemmap when CONFIG_SPARSEMEM_VMEMMAP is configed.
> This makes the user applications (crash, etc) get faster
> pfn_to_page/page_to_pfn operations too.

Are there Crash or makedupfile patches posted yet to make use of this?

> 
> Signed-off-by: Huang Shijie <shijie@...amperecomputing.com>
> ---
>  kernel/crash_core.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index efe87d501c8c..9653c4177191 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -765,6 +765,9 @@ static int __init crash_save_vmcoreinfo_init(void)
>  	VMCOREINFO_SYMBOL(mem_map);
>  	VMCOREINFO_SYMBOL(contig_page_data);
>  #endif
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> +	VMCOREINFO_SYMBOL_ARRAY(vmemmap);
> +#endif
>  #ifdef CONFIG_SPARSEMEM
>  	VMCOREINFO_SYMBOL_ARRAY(mem_section);
>  	VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS);
> -- 
> 2.40.1
>