Re: [Bug fix PATCH v3] Reusing a resource structure allocated bybootmem
From: Yasuaki Ishimatsu
Date: Wed Apr 17 2013 - 02:46:30 EST
Hi David,
2013/04/17 13:47, David Rientjes wrote:
On Wed, 17 Apr 2013, Yasuaki Ishimatsu wrote:
Why not simply do what generic sparsemem support does by testing
PageSlab(virt_to_head_page(res)) and calling kfree() if true and freeing
back to bootmem if false? This should be like a five line patch.
Is your explanation about free_section_usemap()?
If so, I don't think we can release resource structure like
free_section_usemap().
Right, you can't release it like free_section_usemap(), but you're free to
test for PageSlab(virt_to_head_page(res)) in kernel/resource.c.
O.K. I'll update it.
In your explanation case, memmap can be released by put_page_bootmem() in
free_map_bootmem() since all pages of memmap is used only for memmap.
But if my understanding is correct, a page of released resource structure
contain other purpose objects allocated by bootmem. So we cannot
release resource structure like free_section_usemap().
I'm thinking it would be much easier to just suppress the kfree() if
!PageSlab. If you can free an entire page with free_bootmem_late(),
that would be great,
but I'm thinking that will take more work than it's
worth. It seems fine to just do free_bootmem() and leave those pages as
reserved.
I think so, too.
How much memory are we talking about?
Hmm. I don't know correctly.
Here is kernel message of my system. The message is shown by mem_init().
--
Memory: 30491076k/33554432k available (5570k kernel code, 2274228k absent, 789128k reserved, 5667k data, 1784k init)
---
Reserved memroy size is 789128k. So part of them is freed after system boot
by memory hotplug et al.
Thanks,
Yasuaki Ishimatsu
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/