On 05/24/18 at 08:57am, Petr Tesarik wrote: > On Thu, 24 May 2018 09:49:05 +0800 > Dave Young <dyoung@xxxxxxxxxx> wrote: > > > Hi Petr, > > > > On 05/23/18 at 10:22pm, Petr Tesarik wrote: > >[...] > > > In short, if one size fits none, what good is it to hardcode that "one > > > size" into the kernel image? > > > > I agreed with all the things that we can not know the exact memory > > requirement for 100% use cases. But that does not means this is useless > > it is still useful for common use cases of no special and memory hog > > requirements as I mentioned in another reply it can simplify the kdump > > deployment for those people who do not need the special setup. > > I still tend to disagree. This "common-case" reservation depends on > things that are defined by user space. It surely does not make it > easier to build a distribution kernel. Today, I get bug reports that > the number calculated and added to the boot loader configuration by the > installer is inaccurate. If I put a fixed number into a kernel config > option, I will start getting bugs that this number is incorrect (for > some systems). > > > For example, if this is a workstation I just want to break into a shell > > to collect some panic info, then I just need a very minimal initrd, then > > the Kconfig will work just fine. > > What is "a very minimal initrd"? Last time I had to make a significant > adjustment to the estimation for openSUSE, this was caused by growing > user-space requirements (systemd in this case, but I don't want to > start flamewars on that topic, please). > > Anyway, if you want to improve the "common case", then look how IBM > tries to solve it for firmware-assisted dump (fadump) on powerpc: > > https://patchwork.ozlabs.org/patch/905026/ > > The main idea is: > > > Instead of setting aside a significant chunk of memory nobody can use, > > [...] reserve a significant chunk of memory that the kernel is prevented > > from using [...], but applications are free to use it. > > That works great, because user space pages are filtered out in the > common case, so they can be used freely by the panic kernel. This seems a good idea, just makedumpfile need be adjusted since it allows user to decide if dump user space data or not. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
