Is there some method or software that could purposely generate a lot of physical memory fragmentations on linux?

Is there some method or software that could purposely generate a lot of physical memory fragmentations on linux?

[孙世龙 sunshilong]

Hi, list
      Is there some method or software that could purposely generate a lot
of physical memory fragmentations on Linux?

     I need to do some tests under such circumstances.

    Thank you for your attention to this matter.

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Re: Is there some method or software that could purposely generate a lot of physical memory fragmentations on linux?

[Mulyadi Santosa]

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On Tue, Jun 30, 2020 at 1:52 PM 孙世龙 sunshilong <sunshilong369@gmail.com>
wrote:

> Hi, list
>       Is there some method or software that could purposely generate a lot
> of physical memory fragmentations on Linux?
>
>      I need to do some tests under such circumstances.
>
>     Thank you for your attention to this matter.
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies@kernelnewbies.org
> https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>

Hi

Just pseudo idea, if this is in user space, try to:  allocate many blocks
of memory using malloc, each having different size, keep the returned
pointer, then randomly free() some of them, then malloc() again with
different size
-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

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Re: Is there some method or software that could purposely generate a lot of physical memory fragmentations on linux?

[Valdis Klētnieks]

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On Thu, 02 Jul 2020 15:29:18 +0700, Mulyadi Santosa said:

> Just pseudo idea, if this is in user space, try to:  allocate many blocks
> of memory using malloc, each having different size, keep the returned
> pointer, then randomly free() some of them, then malloc() again with
> different size

That will cause userspace malloc() to have fragmentation, but as far
as the kernel is concerned it's all just 4K pages of user memory.

Causing physical memory fragmentation will require abusing the kernel
memory allocators such as kmalloc() and vmalloc() and friends.

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Re: Is there some method or software that could purposely generate a lot of physical memory fragmentations on linux?

[孙世龙 sunshilong]

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Hi, Valdis Klētnieks, Mulyadi Santosa

Thanks to both of you.
>> Just pseudo idea, if this is in user space, try to:  allocate many blocks
>> of memory using malloc, each having different size, keep the returned
>> pointer, then randomly free() some of them, then malloc() again with
>> different size

>That will cause userspace malloc() to have fragmentation, but as far
>as the kernel is concerned it's all just 4K pages of user memory.
>Causing physical memory fragmentation will require abusing the kernel
>memory allocators such as kmalloc() and vmalloc() and friends.

I fully understand what you mean by "cause userspace malloc() to have
fragmentation".
I am sorry, maybe I mislead you. I just want there are no available free
high order blocks(i.e
32KB,64KB, 128KB and etc) on the platform.
How can I more efficiently and automatically achieve this goal?

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