On 01.08.2016 14:14, Ralf-Peter Rohbeck wrote:
On 01.08.2016 13:26, Michal Hocko wrote:
sdc, sdd and sde each at max speed, with a little bit of garden
variety IO
on sda and sdb.
So do I get it right that the majority of the IO is to those slower USB
disks? If yes then does lowering the dirty_bytes to something smaller
help?
Yes, the vast majority.
I set dirty_bytes to 128MiB and started a fairly IO and memory
intensive process and the OOM killer kicked in within a few seconds.
Same with 16MiB dirty_bytes and 1MiB.
Some additional IO load from my fast subsystem is enough:
At 1MiB dirty_bytes,
find /btrfs0/ -type f -exec md5sum {} \;
was enough (where /btrfs0 is on a LVM2 LV and the PV is on sda.) It
read a few dozen files (random stuff with very mixed file sizes, none
very big) until the OOM killer kicked in.
I'll try 4.6.
With Debian 4.6.0.1 (4.6.4-1) it works: Writing to 3 USB drives and
running each of the 3 tests that triggered the OOM killer in parallel,
with default dirty settings.
Ralf-Peter
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