Messages in this thread | | | Subject | Re: [Patch] kexec: increase max of kexec segments and use dynamic allocation | From | (Eric W. Biederman) | Date | Sat, 24 Jul 2010 19:54:22 -0700 |
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huang ying <huang.ying.caritas@gmail.com> writes:
> On Thu, Jul 22, 2010 at 3:08 PM, Eric W. Biederman > <ebiederm@xmission.com> wrote: >> Cong Wang <amwang@redhat.com> writes: >> >>> On 07/22/10 14:28, Eric W. Biederman wrote: >>>> Amerigo Wang<amwang@redhat.com> writes: >>>> >>>>> Currently KEXEC_SEGMENT_MAX is only 16 which is too small for machine with >>>>> many memory ranges. Increase this hard limit to 1024 which is reasonably large, >>>>> and change ->segment from a static array to a dynamically allocated memory. >>>> >>>> ??? >>>> >>>> This should be about segments in the executable being loaded. What >>>> executable has one segment for each range of physical memory? >>>> >>>> Not that generalizing this is a bad idea but with a comment that >>>> seems entirely wrong I am wondering what the problem really is. >>>> >>> >>> Ah, I think Neil should explain this. >>> >>> He made a patch which includes many memory ranges, caused kexec >>> fails to load the kernel. Increasing this limit and the corresponding >>> one in kexec-tools fixes the problem. His patch is not in upstream >>> kexec-tools, AFAIK. >>> >>> However, even if we don't consider that patch, isn't 16 too small too? >> >> Generally you just need one physical hunk for the code, maybe a second >> for the initrd. >> >> It is perfectly fine to raise the number of segments as it doesn't >> affect the ABI, but it wants a good explanation of what kind of weird >> application wants to write to all over memory when it is loaded. > > kexec can be used to load not only the kernel images, but also more > complex images such as hibernation image. So I think it is good to > raise the number of segments.
Totally reasonable.
And in all fairness the patch does a good job of raising the limit.
However if that is the goal 1024 is probably a bit low as I believe SGI has built machines with that many nodes. Still after the patch under discussion 1024 was only a limit in a header file so it can be trivially changed.
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