Re: [PATCH 1/1] mm/khugepaged: bypassing unnecessary scans with MMF_DISABLE_THP check

[Lance Yang]

On Tue, Jan 30, 2024 at 5:35 PM Michal Hocko <mhocko@xxxxxxxx> wrote:
>
> On Tue 30-01-24 11:08:10, Lance Yang wrote:
> > On Tue, Jan 30, 2024 at 10:12 AM Lance Yang <ioworker0@xxxxxxxxx> wrote:
> > >
> > > Hey Michal,
> > >
> > > Thanks for taking time to review!
> > >
> > > On some servers within our company, we deploy a
> > > daemon responsible for monitoring and updating
> > > local applications. Some applications prefer not to
> > > use THP, so the daemon calls prctl to disable THP
> > > before fork/exec. Conversely, for other applications,
> > > the daemon calls prctl to enable THP before fork/exec.
> > >
> > > Ideally, the daemon should invoke prctl after the fork,
> > > but its current implementation follows the described
> > > approach.
> >
> > In the Go standard library, there is no direct encapsulation
> > of the fork system call. Instead, fork and execve are
> > combined into one through syscall.ForkExec.
>
> OK, this is an important detail. Something that should be a part
> of the chnagelog. It is also important to note that this is not
> a correctness issue but rather an optimization to save expensive
> checks on each VMA when userspace cannot prctl itself before spawning
> into the new process.

Thanks for pointing that out!

I'll include it in the changelog. Good to know it's an optimization
rather than a correctness issue.

Thanks,
Lance

> --
> Michal Hocko
> SUSE Labs