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From: Lance Yang <ioworker0@gmail.com>
Date: Wed, 31 Jan 2024 08:37:20 +0800
Message-ID: <CAK1f24kLYK-yCQQJO7eJbuMwg02TLi8C_SeES3fbqAOgQ4AAjQ@mail.gmail.com>
Subject: Re: [PATCH 1/1] mm/khugepaged: bypassing unnecessary scans with
 MMF_DISABLE_THP check
To: Michal Hocko <mhocko@suse.com>, "Zach O'Keefe" <zokeefe@google.com>, Yang Shi <shy828301@gmail.com>
Cc: akpm@linux-foundation.org, david@redhat.com, songmuchun@bytedance.com, 
	peterx@redhat.com, minchan@kernel.org, linux-mm@kvack.org, 
	linux-kernel@vger.kernel.org
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Hey Zach and Yang,

Could I start a new version?

Thanks,
Lance

On Tue, Jan 30, 2024 at 5:46=E2=80=AFPM Lance Yang <ioworker0@gmail.com> wr=
ote:
>
> On Tue, Jan 30, 2024 at 5:35=E2=80=AFPM Michal Hocko <mhocko@suse.com> wr=
ote:
> >
> > On Tue 30-01-24 11:08:10, Lance Yang wrote:
> > > On Tue, Jan 30, 2024 at 10:12=E2=80=AFAM Lance Yang <ioworker0@gmail.=
com> 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