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Subject: Re: ODEBUG: Out of memory. ODEBUG disabled
From:   Qian Cai <cai@gmx.us>
In-Reply-To: <trinity-0da197a3-0f6e-41a3-8ab7-a3519e158a88-1541859073829@msvc-mesg-gmx023>
Date:   Mon, 12 Nov 2018 23:33:01 -0500
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Zhong Jiang <zhongjiang@huawei.com>,
        linux kernel <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>
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Message-Id: <FE1B58AA-FC0E-4E0A-8A76-F98B70548F36@gmx.us>
References: <trinity-be6414fb-25ba-4881-acc6-abe3b375d0d0-1541814329304@msvc-mesg-gmx021>
 <c7b58543-ffd2-44bb-1005-e9733782bad5@redhat.com>
 <trinity-0da197a3-0f6e-41a3-8ab7-a3519e158a88-1541859073829@msvc-mesg-gmx023>
To:     Waiman Long <longman@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
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> On Nov 10, 2018, at 9:11 AM, Qian Cai <cai@gmx.us> wrote:
> 
> On 11/10/18 at 8:59 AM, Waiman Long wrote:
> 
>> On 11/09/2018 08:45 PM, Qian Cai wrote:
>>>> Sent: Friday, November 09, 2018 at 5:08 PM
>>>> From: "Waiman Long" <longman@redhat.com>
>>>> To: "Qian Cai" <cai@gmx.us>, "Yang Shi" <yang.shi@linux.alibaba.com>
>>>> Cc: "open list" <linux-kernel@vger.kernel.org>, "Thomas Gleixner" <tglx@linutronix.de>, "Arnd Bergmann" <arnd@arndb.de>, "Joel Fernandes (Google)" <joel@joelfernandes.org>, "Zhong Jiang" <zhongjiang@huawei.com>
>>>> Subject: Re: ODEBUG: Out of memory. ODEBUG disabled
>>>> 
>>>> On 11/09/2018 04:51 PM, Qian Cai wrote:
>>>>>> On Nov 9, 2018, at 4:42 PM, Yang Shi <yang.shi@linux.alibaba.com> wrote:
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> On 11/9/18 1:36 PM, Qian Cai wrote:
>>>>>>> It is a bit annoying on this aarch64 server with 64 CPUs that is
>>>>>>> booting the latest mainline (3541833fd1f2) causes object debugging
>>>>>>> always running out of memory.
>>>>>> May you please paste the detail failure log?
>>>>> I assume you mean dmesg.
>>>>> 
>>>>> Here is the dmesg for 64 CPUs,
>>>>> https://paste.ubuntu.com/p/BnhvXXhn7k/
>>>>>>> I have to boot the kernel with only 16 CPUs instead (nr_cpus=16)
>>>>>>> to make it work. Is it expected that object debugging is not going
>>>>>>> to work with large machines?
>>>>>> I don't think so. I'm supposed it works well with large CPU number on x86.
>>>>> Here is the one with nr_cpus workaround,
>>>>> https://paste.ubuntu.com/p/qMpd2CCPSV/
>>>> The debugobjects code have a set of 1024 statically allocated debug
>>>> objects that can be used in early boot before the slab memory allocator
>>>> is initialized. Apparently, the system may have used up all the
>>>> statically allocated objects. Try double ODEBUG_POOL_SIZE to see if it
>>>> helps.
>>> Great, you are right. Doubling the size makes it work. Does it make sense
>>> to have a kconfig option instead?
>> 
>> First, I think you need to figure out what your system needed to use up
>> so many debug objects in early boot. If there is a legitimate reason for
>> this behavior, we can talk about having a kconfig option to increase that.
> Anybody else not getting ODEBUG OOM with more than 64-CPU? As
> mentioned, restricting to 16-CPU works fine. How can I figure out why the
> system uses so much debug objects?
On another aarch64 server with 256-CPU, even double the size of
ODEBUG_POOL_SIZE, i.e., 2048 will get "ODEBUG: Out of memory. ODEBUG
disabled”.