linux-kernel - Re: [PATCH v5 2/2] lib: stackdepot: Add support to disable stack depot

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Message-ID: <YAobhDFEJKa26OwH@google.com>
Date:   Thu, 21 Jan 2021 16:25:40 -0800
From:   Minchan Kim <minchan@...nel.org>
To:     vjitta@...eaurora.org
Cc:     glider@...gle.com, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, broonie@...nel.org, mhiramat@...nel.org,
        linux-kernel@...r.kernel.org, ylal@...eaurora.org,
        vinmenon@...eaurora.org
Subject: Re: [PATCH v5 2/2] lib: stackdepot: Add support to disable stack
 depot

On Mon, Jan 18, 2021 at 03:26:42PM +0530, vjitta@...eaurora.org wrote:
> From: Vijayanand Jitta <vjitta@...eaurora.org>
> 
> Add a kernel parameter stack_depot_disable to disable
> stack depot. So that stack hash table doesn't consume
> any memory when stack depot is disabled.

The usecase is CONFIG_PAGE_OWNER without page_owner=on.
Without this patch, stackdepot will consume the memory
for the hashtable. By default, it's 8M which is never trivial.

With this option, in CONFIG_PAGE_OWNER configured system,
page_owner=off, stack_depot_disable in kernel command line,
we could save the wasted memory for the hashtable.

> 
> Signed-off-by: Vinayak Menon <vinmenon@...eaurora.org>
> Signed-off-by: Vijayanand Jitta <vjitta@...eaurora.org>

Please also update kernel-parameters.txt.

> ---
>  include/linux/stackdepot.h |  1 +
>  init/main.c                |  2 ++
>  lib/stackdepot.c           | 33 +++++++++++++++++++++++++++++----
>  3 files changed, 32 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
> index 24d49c7..eafd9aa 100644
> --- a/include/linux/stackdepot.h
> +++ b/include/linux/stackdepot.h
> @@ -21,4 +21,5 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
>  
>  unsigned int filter_irq_stacks(unsigned long *entries, unsigned int nr_entries);
>  
> +int stack_depot_init(void);
>  #endif
> diff --git a/init/main.c b/init/main.c
> index 32b2a8a..8fcf9bb 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -98,6 +98,7 @@
>  #include <linux/mem_encrypt.h>
>  #include <linux/kcsan.h>
>  #include <linux/init_syscalls.h>
> +#include <linux/stackdepot.h>
>  
>  #include <asm/io.h>
>  #include <asm/bugs.h>
> @@ -827,6 +828,7 @@ static void __init mm_init(void)
>  	page_ext_init_flatmem();
>  	init_debug_pagealloc();
>  	report_meminit();
> +	stack_depot_init();
>  	mem_init();
>  	kmem_cache_init();
>  	kmemleak_init();
> diff --git a/lib/stackdepot.c b/lib/stackdepot.c
> index dff8521..d20e6fd 100644
> --- a/lib/stackdepot.c
> +++ b/lib/stackdepot.c
> @@ -31,6 +31,8 @@
>  #include <linux/stackdepot.h>
>  #include <linux/string.h>
>  #include <linux/types.h>
> +#include <linux/vmalloc.h>

Why do we need vmalloc?

Otherwise, looks good to me.
Thank you!