Messages in this thread | | | Date | Tue, 14 Nov 2017 15:53:27 +0000 | From | Mel Gorman <> | Subject | Re: Allocation failure of ring buffer for trace |
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On Tue, Nov 14, 2017 at 10:39:19AM -0500, YASUAKI ISHIMATSU wrote: > > > On 11/14/2017 06:46 AM, Mel Gorman wrote: > > On Mon, Nov 13, 2017 at 12:48:36PM -0500, YASUAKI ISHIMATSU wrote: > >> When using trace_buf_size= boot option, memory allocation of ring buffer > >> for trace fails as follows: > >> > >> [ ] x86: Booting SMP configuration: > >> <SNIP> > >> > >> In my server, there are 384 CPUs, 512 GB memory and 8 nodes. And > >> "trace_buf_size=100M" is set. > >> > >> When using trace_buf_size=100M, kernel allocates 100 MB memory > >> per CPU before calling free_are_init_core(). Kernel tries to > >> allocates 38.4GB (100 MB * 384 CPU) memory. But available memory > >> at this time is about 16GB (2 GB * 8 nodes) due to the following commit: > >> > >> 3a80a7fa7989 ("mm: meminit: initialise a subset of struct pages > >> if CONFIG_DEFERRED_STRUCT_PAGE_INIT is set") > >> > > > > 1. What is the use case for such a large trace buffer being allocated at > > boot time? > > I'm not sure the use case. I found the following commit log: > > commit 864b9a393dcb5aed09b8fd31b9bbda0fdda99374 > Author: Michal Hocko <mhocko@suse.com> > Date: Fri Jun 2 14:46:49 2017 -0700 > > mm: consider memblock reservations for deferred memory initialization sizing > > So I thought similar memory exhaustion may occurs on other boot option. > And I reproduced the issue. >
That was different, it was a premature OOM caused by reservations that were of a known size. It's not related to trace_buf_size in any fashion.
> > > 2. Is disabling CONFIG_DEFERRED_STRUCT_PAGE_INIT at compile time an > > option for you given that it's a custom-built kernel and not a > > distribution kernel? > > The issue also occurred on distribution kernels. So we have to fix the issue. >
I'm aware of now bugs against a distribution kernel. However, does the patch work for you?
-- Mel Gorman SUSE Labs
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