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From:   Punit Agrawal <punit.agrawal@arm.com>
To:     Jonathan Cameron <jonathan.cameron@huawei.com>
Cc:     Michal Hocko <mhocko@kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
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        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Will Deacon <will.deacon@arm.com>,
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        Andrew Morton <akpm@linux-foundation.org>,
        zhongjiang <zhongjiang@huawei.com>, <wanghuiqiang@huawei.com>
Subject: Re: [PATCH 1/2] arm64: avoid alloc memory on offline node
In-Reply-To: <20180622184223.00007bc3@huawei.com> (Jonathan Cameron's message
        of "Fri, 22 Jun 2018 18:42:23 +0100")
References: <20180619120714.GE13685@dhcp22.suse.cz>
        <874lhz3pmn.fsf@e105922-lin.cambridge.arm.com>
        <20180619140818.GA16927@e107981-ln.cambridge.arm.com>
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        <20180619151425.GH13685@dhcp22.suse.cz>
        <87r2l23i2b.fsf@e105922-lin.cambridge.arm.com>
        <20180619163256.GA18952@e107981-ln.cambridge.arm.com>
        <814205eb-ae86-a519-bed0-f09b8e2d3a02@huawei.com>
        <87602d3ccl.fsf@e105922-lin.cambridge.arm.com>
        <5c083c9c-473f-f504-848b-48506d0fd380@huawei.com>
        <20180622091153.GU10465@dhcp22.suse.cz>
        <87y3f7yv89.fsf@e105922-lin.cambridge.arm.com>
        <20180622184223.00007bc3@huawei.com>
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Date:   Tue, 26 Jun 2018 18:27:13 +0100
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Jonathan Cameron <jonathan.cameron@huawei.com> writes:

[...]

>
> I'll test it when back in the office, but I had a similar issue with
> memory only nodes when I moved the SRAT listing for cpus from the 4
> 4th mode to the 3rd node to fake some memory I could hot unplug.
> This gave a memory only node for the last node on the system.
>
> When I instead moved cpus from the 3rd node to the 4th (so the node
> with only memory was now in the middle, everything worked).
>
> Was odd, and I'd been meaning to chase it down but hadn't gotten to it
> yet.  If I get time I'll put together some test firmwares as see if there
> are any other nasty corner cases we aren't handling.

If you get a chance, it'd be really helpful to test reversing the
ordering of entries in the SRAT and booting with a restricted
NR_CPUS.

This issue was found through code inspection.

Please make sure to use the updated patch from Lorenzo for your
tests[0].

[0] https://marc.info/?l=linux-acpi&m=152998665713983&w=2

>
> Jonathan
>
>> 
>> _______________________________________________
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