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Date:      Mon, 4 Mar 2019 15:26:39 +0000
From:      Edward Napierala <trasz@freebsd.org>
To:        Cy Schubert <Cy.Schubert@cschubert.com>
Cc:        Konstantin Belousov <kostikbel@gmail.com>, src-committers <src-committers@freebsd.org>,  svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   Re: svn commit: r344758 - in head/sys/fs: nfs nfsserver
Message-ID:  <CAFLM3-pFi_-yhMx4bhm_0S5FK3BdLh1xbXV%2BcKgPks7d8cttMw@mail.gmail.com>
In-Reply-To: <FF146246-2FFD-4FC7-9720-7D72D1AFEB29@cschubert.com>
References:  <201903041302.x24D2aG0093620@repo.freebsd.org> <20190304132021.GN68879@kib.kiev.ua> <CAFLM3-pLSQ8sBawC9YBTgxdMKhtNtoQG1bn2QVDuw-2tDKb4Gg@mail.gmail.com> <20190304143021.GO68879@kib.kiev.ua> <FF146246-2FFD-4FC7-9720-7D72D1AFEB29@cschubert.com>

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pon., 4 mar 2019 o 15:17 Cy Schubert <Cy.Schubert@cschubert.com> napisa=C5=
=82(a):
>
> On March 4, 2019 6:30:21 AM PST, Konstantin Belousov <kostikbel@gmail.com=
> wrote:
> >On Mon, Mar 04, 2019 at 01:31:37PM +0000, Edward Napierala wrote:
> >> pon., 4 mar 2019 o 13:20 Konstantin Belousov <kostikbel@gmail.com>
> >napisa=C5=82(a):
> >> > > +     p =3D curthread;
> >> > Why do you name it 'p', which is typical for process, and not 'td',
> >you are
> >> > changing most of the code anyway.
> >>
> >> To keep the diff size smaller.  You're right, this touches a lot of
> >stuff,
> >> but most of those added lines are temporary anyway - they will be
> >> removed later, when the td is pushed down even more.
> >But if you create code churn, doing it only half way is worse.
> >
> >>
> >> > Also I am curious why. It is certainly fine to remove td when it is
> >used
> >> > as a formal placeholder argument only. But when the first action in
> >the
> >> > function is evaluation of curthread() it becomes less obvious.
> >>
> >> Again, many/most of those are temporary.  I'm trying to push td down
> >> in small steps, "layer by layer", so it's easy to review.
> >>
> >> > curthread() become very cheap on modern amd64, I am not so sure
> >about
> >> > older machines or non-x86 cases.
> >>
> >> The main reason is readability.  Right now there's no easy way to
> >tell whether
> >> a function can be passed any td, or if it must be curthread.
> >I must admit that this is the weirdnest argument against 'td' that I
> >ever
> >heard.  I saw more or less reasonable argumentation
> >- that using less arguments make one more register for argument passing
> >  (amd64 has 6 input arg regs),
> >- that less arguments make smaller call code.
> >But trust me, in all cases where function can take td !=3D curthread, it
> >is
> >either obvious or well-known for anybody who works with that code.
> >
> >Before you start doing a lot of small changes (AKA continous churn)
> >please formulate your goals and get some public feedback.  My immediate
> >question that I want answered before you ever start touching the code,
> >is what you plan to do with
> >       sys_syscall(struct thread *td, uap)
>
> Agreed on all points. At the very least this group of commits should be r=
eviewed on phabricator.

It has been, even though they are pretty much mechanical changes.

> Can we back all these commits out until there is a proper review, please?

The review from the NFS maintainer is not enough?



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