Andrew Morton akpm@linux-foundation.org writes:

On Thu, 6 Apr 2023 09:53:37 -0700 Stefan Roesch shr@devkernel.io wrote:

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So far KSM can only be enabled by calling madvise for memory regions. To be able to use KSM for more workloads, KSM needs to have the ability to be enabled / disabled at the process / cgroup level.

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@@ -53,6 +62,18 @@ void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);

#else /* !CONFIG_KSM */

+static inline int ksm_add_mm(struct mm_struct *mm) +{ +}

The compiler doesn't like the lack of a return value.

I queued up a patch to simply delete the above function - seems that ksm_add_mm() has no callers if CONFIG_KSM=n.

The same might be true of the ksm_add_vma()...ksm_exit() stubs also, Perhaps some kind soul could take a look at whether we can simply clean those out.

ksm_add_mm() and ksm_add_vmas() is not needed. However ksm_add_vma() is required. It is called from mm/mmap.c