Re: [PATCH v4 5/8] vmcore: copy ELF note segments in the 2nd kernelper page vmcore objects
From: HATAYAMA Daisuke
Date: Wed May 08 2013 - 00:58:51 EST
(2013/05/08 0:08), Vivek Goyal wrote:
On Tue, May 07, 2013 at 04:56:46PM +0900, HATAYAMA Daisuke wrote:
(2013/04/30 4:36), Vivek Goyal wrote:
On Sat, Apr 13, 2013 at 09:21:33AM +0900, HATAYAMA Daisuke wrote:
[..]
ELF notes are per-cpu, so total size of ELF note segments increases
according to the number of CPUs. The current maximum number of CPUs on
x86_64 is 5192, and there's already system with 4192 CPUs in SGI,
where total size amounts to 1MB. This can be larger in the neare
futrue or possibly even now on another architecture. Thus, to avoid
the case where memory allocation for large block fails, we allocate
vmcore objects per pages.
IIRC, eric had suggested using vmalloc() and remap_vmalloc_range(). What's
wrong with that? That should keep your vc_list relatively smaller.
Yes, it's handy if it's possible to remap them in vmalloc space, but
the problem here is that remap_vmalloc_range requires the first
argument vma to cover full range of the requested map. This becomes
problem when requested area for mmap() overlaps multiple objects,
for example, ELF headers and memory refered to by the first PT_LOAD
program header.
To use remap_vmalloc_range, it's necessary to prepare a new variant
similar to remap_pfn_range by which we can remap different objects
separately to a single vma.
Ok. Is it hard to prepare one such variant. If we can write one, it will
simplify the vmcore code.
I'll try to write it. Although I avoided implementing it once, now it
looks relatively easy to implement thanks to vm_insert_page, which does
all essential thing. All I have to do should be consider sanity-check only.
--
Thanks.
HATAYAMA, Daisuke
--
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/