Re: [RFC] mm: show message when updating min_free_kbytes in thp

David Rientjes
2014-01-02T21:58:57Z

On Thu, 2 Jan 2014, Dave Hansen wrote:

> > min_free_kbytes may be updated during thp's initialization. Sometimes,
> > this will change the value being set by user. Showing message will
> > clarify this confusion.
> ...
> > - if (recommended_min > min_free_kbytes)
> > + if (recommended_min > min_free_kbytes) {
> > min_free_kbytes = recommended_min;
> > + pr_info("min_free_kbytes is updated to %d by enabling transparent hugepage.\n",
> > + min_free_kbytes);
> > + }
>
> "updated" doesn't tell us much. It's also kinda nasty that if we enable
> then disable THP, we end up with an elevated min_free_kbytes. Maybe we
> should at least put something in that tells the user how to get back
> where they were if they care:
>

The default value of min_free_kbytes depends on the implementation of the
VM regardless of any config options that you may have enabled. We don't
specify what the non-thp default is in the kernel log, so why do we need
to specify what the thp default is?