Re: [Patch 0/7] Implement crashkernel=auto

Amerigo Wang
2009-08-06T03:37:53Z

Eric W. Biederman wrote:
> In general I figure that whoever builds the kernel and initrd should be
> responsible for testing and figuring out the amount of memory needed.
> The primary kernel has no idea what is going to loaded in there and
> as such no real idea how much memory is needed.
>

Yeah, that is exactly why I _didn't_ pick the idea of reserving memory
automatically and silently without "crashkernel=auto".

If a user specifies "crashkernel=auto", that means he/she has no idea
how much memory to be reserved, he/she wants to let the kernel to
decide. Kernel should know better than the user in this situation.

>>> You also have to build (or at least load) the whole kdump image after
>>> the system boots, and configure someplace for this to be saved.
>>>
>>> What class of problems do you expect to catch with this?
>>>
>>>
>> Again, try to save the user from choosing numbers for "crashkernel=".
>>
>
> The user being kernel developers? Whoever builds the kernel and initrd
> should be responsible for testing and figuring this out.
>
> In a distro context installers etc should be able to setup good defaults
> so end users don't have to worry about this.
>
>
For kernel developers, "crashkernel=auto" should save a lot. You seem
agree with this one.

For users, they rely on the distro which can always specify
"crashkernel=auto" now, not different numbers for different arch, since
"crashkernel=auto" is designed to be safe for all cases. Also saves many
work...

>>> What has me puzzled is that the mkdumprd that ships with fedora isn't
>>> usable without patching, and it seems to be steadily getting worse.
>>>
>> Please explain why it is not usable? The patch won't break the userspace, since
>> it modifies the "crashkernel=" command line dynamically.
>>
>
> No the crashdump mechanism is useless because user space is already
> broken and unusable.

Again, why broken?

Thanks.