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 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
