On 14/10/2019 15:25, Mike Kravetz wrote: > [...] > I don't know much about early_param(), so I will assume this works as you > describe. However, a quick grep shows hugepage options for ia64 also with > early_param. > Thanks a lot for the prompt and quite informative reply Mike. I've checked this IA64 parameter after your mention, and it just sets the hugepages size, I don't think it'll affect the purpose of this patch. >> * The return when sysctl handler is prevented to progress due to >> nohugepages is -EINVAL, but could be changed; I've just followed >> present code there, but I'm OK changing that if we have suggestions. > > It looks like you only have short circuited/prevented nr_hugepages via > sysfs/sysctl. Theoretically, one could set nr_overcommit_hugepages and > still allocate hugetlb pages. So, if you REALLY want to shut things down > you need to stop this as well. > > There is already a macro hugepages_supported() that can be set by arch > specific code. I wonder how difficult it would be to 'overwrite' the > macro if nohugepages is specified. Perhaps just a level of naming > indirection. This would use the existing code to prevent all hugetlb usage. > Outstanding! It's a much better idea to use hugepages_supported() infrastructure, it prevents even the creation of hugepages-related sysfs entries; I've worked a V2 with this modification, and it worked fine, thanks for the suggestion. > It seems like there may be some discussion about 'the right' way to > do kdump. I can't add to that discussion, but if such an option as > nohugepages is needed, I can help. > I think this parameter may be important/useful not only for kdump - it is a legitimate way of disabling hugepages, something we don't currently have on kernel. I'll submit a V2, for Ubuntu kdump specially this is quite helpful! Cheers, Guilherme
