Am Fr., 2. Nov. 2018 um 14:13 Uhr schrieb Vlastimil Babka [off-list ref]:

On 11/2/18 1:41 PM, Marinko Catovic wrote:

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any idea how to find out what that might be? I'd really have no idea,
I also wonder why this never was an issue with 3.x
find uses regex patterns, that's the only thing that may be unusual.

The allocation tracepoint has the stack trace so that might help. This

Well we already checked the mm_page_alloc traces and it seemed that only
THP allocations could be the culprit. But apparently defrag=defer made
no difference. I would still recommend it so we can see the effects on
the traces. And adding tracepoints
compaction/mm_compaction_try_to_compact_pages and
compaction/mm_compaction_suitable as I suggested should show which
high-order allocations actually invoke the compaction.

Anything in particular I should do to figure this out?

Setup the same monitoring as before, but with two additional tracepoints
(echo 1 > .../enable) and once the problem appears, provide the tracing
output.

I think I'll need more details about that setup  :)
also, do you want the tracing output every 5sec or just once when it
is around the worst case? what files exactly?