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Date:      Mon, 26 Aug 2019 19:34:39 +0300
From:      Konstantin Belousov <kostikbel@gmail.com>
To:        John Baldwin <jhb@FreeBSD.org>
Cc:        Conrad Meyer <cem@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all <svn-src-all@freebsd.org>, svn-src-head <svn-src-head@freebsd.org>
Subject:   Re: svn commit: r351456 - head/sys/amd64/amd64
Message-ID:  <20190826163439.GS71821@kib.kiev.ua>
In-Reply-To: <1a09a4ef-45aa-1bb2-5b16-1bde24df0f3d@FreeBSD.org>
References:  <201908241528.x7OFSemm026182@repo.freebsd.org> <CAG6CVpWN56eRRUgCubK3F750zoDun8ZocLaot5w0H4Emrq9=xQ@mail.gmail.com> <20190824161503.GA71821@kib.kiev.ua> <CAG6CVpWMquckqAx7jQTam5qjB3GubrrzQYxnZafjwjLEjqf6Qg@mail.gmail.com> <20190824204353.GH71821@kib.kiev.ua> <1a09a4ef-45aa-1bb2-5b16-1bde24df0f3d@FreeBSD.org>

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On Mon, Aug 26, 2019 at 09:25:11AM -0700, John Baldwin wrote:
> On 8/24/19 1:43 PM, Konstantin Belousov wrote:
> > On Sat, Aug 24, 2019 at 11:47:52AM -0700, Conrad Meyer wrote:
> >> On Sat, Aug 24, 2019 at 9:15 AM Konstantin Belousov <kostikbel@gmail.com> wrote:
> >>>
> >>> On Sat, Aug 24, 2019 at 08:49:42AM -0700, Conrad Meyer wrote:
> >>>> Hi Konstantin,
> >>>>
> >>>> What is the motivation for this change?  The commit message doesn't
> >>>> really describe why it was done.
> >>>
> >>> Really it does. There is no point to request allocations for e.g.
> >>> doublefault stack to be at the local domain, because this stack is only
> >>> used once.  Doublefault is definitely a machine halt situation, it does
> >>> not matter if it generates inter-socket traffic to handle.
> >>>
> >>> Same for boot stacks, and for mce.
> >>>
> >>> The change avoids unnecessary constraints.
> >>
> >> Sure, but what is the harm of the unnecessary constraints?  Does this
> >> change fix an actual bug, or is it just a stylistic preference to
> >> avoid domain-specific allocations for infrequently used objects?
> > I am not sure about this being a stylistic preference.  We usually
> > write code to express the required actions.  I removed constraints
> > which did not added anything neither to code correctness nor to the
> > performance.
> 
> Judging by the thread on current though, this fixes boot panics on
> machines with NUMA but CPUs that don't have local memory, correct?
> I think that's the thing Conrad is asking.
> 
This was discovered later.



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