Messages in this thread | | | Date | Tue, 12 Jul 2016 14:42:12 +0200 | From | Matthias Dahl <> | Subject | Re: Page Allocation Failures/OOM with dm-crypt on software RAID10 (Intel Rapid Storage) |
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Hello Michal...
On 2016-07-12 13:49, Michal Hocko wrote:
> I am not a storage expert (not even mention dm-crypt). But what those > counters say is that the IO completion doesn't trigger so the > PageWriteback flag is still set. Such a page is not reclaimable > obviously. So I would check the IO delivery path and focus on the > potential dm-crypt involvement if you suspect this is a contributing > factor.
Sounds reasonable... except that I have no clue how to trace that with the limited means I have at my disposal right now and with the limited knowledge I have of the kernel internals. ;-)
> Who is consuming those objects? Where is the rest 70% of memory hiding?
Is there any way to get a more detailed listing of where the memory is spent while dd is running? Something I could pipe every 500ms or so for later analysis or so?
> Writer will get throttled but the concurrent memory consumer will not > normally. So you can end up in this situation.
Hm, okay. I am still confused though: If I, for example, let dd do the exact same thing on a raw partition on the RAID10, nothing like that happens. Wouldn't we have the same race and problem then too...? It is only with dm-crypt in-between that all of this shows itself. But I do somehow suspect the RAID10 Intel Rapid Storage to be the cause or at least partially.
Like I said, if you have any pointers how I could further trace this or figure out who is exactly consuming what memory, that would be very helpful... Thanks.
So long, Matthias
-- Dipl.-Inf. (FH) Matthias Dahl | Software Engineer | binary-island.eu services: custom software [desktop, mobile, web], server administration
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