Messages in this thread | | | Subject | Re: ODEBUG: Out of memory. ODEBUG disabled | From | Qian Cai <> | Date | Tue, 13 Nov 2018 19:55:55 -0500 |
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> On Nov 12, 2018, at 11:33 PM, Qian Cai <cai@gmx.us> wrote: > > > >> 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”.
OK, here is the problem.
In order to get aarch64 work, the initial ODEBUG_POOL_SIZE on
64-CPU: need 2048 256-CPU: need 8192 (4096 too small)
This commit 97dd552eb23c
+ * Increase the thresholds for allocating and freeing objects + * according to the number of possible CPUs available in the system. + */ + debug_objects_pool_size += num_possible_cpus() * 32;
Why magic number 32?
It needs to be bigger than that for aarch64.
(2048 + 64 x 32 - 1024) / 64 = 48 (work on 64-cpu) (4096 + 256 x 32 - 1024) / 256 = 48 (not work on 256-cpu) (8196 + 256 x 32 - 1024) / 256 = 60 (work on 256-cpu)
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