vm.dirty_background_ratio=5 didn't help. But echo 3 > /proc/sys/vm/drop_caches "clears" the issue for a few minutes, until the cache is full again.
So far I've seen the issue in 3 installations; all of them were 32bit with 16+ GB RAM; maybe that is the key point here. And none of them had issues in older, 4.2- kernels. Here is my new test case, which should reproduce the issue without some special setup. It basically copies /lib around: # echo 3 > /proc/sys/vm/drop_caches # s=/lib; d=1; rm -rf "$d"; echo -n "Copying $s to $d: "; while /usr/bin/time -f %e cp -a "$s" "$d"; do s=$d; d=$((($d+1)%10)); rm -rf "$d"; echo -n "Copying $s to $d: "; done Copying /lib to 1: 8.61 Copying 1 to 2: 9.59 Copying 2 to 3: 10.01 Copying 3 to 4: 10.09 Copying 4 to 5: 10.39 Copying 5 to 6: 10.31 Copying 6 to 7: 11.79 Copying 7 to 8: 12.70 Copying 8 to 9: 14.26 Copying 9 to 0: 14.95 Copying 0 to 1: 21.04 Copying 1 to 2: 57.64 Copying 2 to 3: 383.68 Copying 3 to 4: 420.04 Copying 4 to 5: 377.91 Copying 5 to 6: 434.98 ... -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1698118 Title: Slow disk writes after some uptime, only on certain hw and 4.4+ kernels To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-hwe/+bug/1698118/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
