IMPALA-5220: memory maintenance cleanup
Remove logic that tries to release pages from TcMalloc's page heap:
TCMalloc's behaviour changed so that it automatically does this with
"aggressive decommit" and committed spans can't accumulate in the page
Also increase the memory maintenance interval - 1s is too aggressive and
can free memory that will be imminently reused by a running query, e.g.
particularly buffer pool buffers.
Tried to reproduce
IMPALA-2800 in a couple of ways:
- Ran a big aggregation locally and cancelled it
- Looked at memz/ of some live clusters (production and stress test).
In all cases "Bytes in page heap freelist" was 0.
This confirms that
IMPALA-2800 was already solved, probably
by the gperftools 2.5 upgrade, where aggressive decommit
would mean that memory is released to the system in
free() instead of the ReleaseFreeMemory() callst.
I was able to confirm that the ReleaseFreeMemory() calls were unnecessary
to avoid retaining memory by running a couple of stress tests
locally with this patch and checking that "Bytes in page
heap freelist" was 0 after the change and that memory consumption
was generally sensible.
Reviewed-by: Tim Armstrong <email@example.com>
Tested-by: Impala Public Jenkins