In my old system, I was already having desktop freezes on some heavy I/O operations like
apt-get dist-upgrade and copying 4 GB video files. But now, it has become a lot worse: any
apt-get install is enough the freeze the whole desktop, and copying the videos with
nice -c 3 does not help at all, I cannot do any operation for minutes. According to
man ionice, the impact of an idle I/O process on normal system activity should be zero.
One weird swap problem appeared as well: I had disabled the swap partition, and twice an OOM was triggered. But instead of killing the process that trigerred the OOM (I set
vm.oom_kill_allocating_task=1), the disk started spinning and totally froze the desktop for a long time, although I had run
sudo swapoff -a and checked whether it worked.
The old hardware and system:
- Hard drive: 500 GB Toshiba
- System: Debian 7.9 (32 bits)
- Kernel: 3.15.10-zen-686 (Liquorix)
- Disk scheduler: BFQ
- Filesystem: ext4
The new hardware and system:
- Hard drive: 1 TB Samsung
- System: Ubuntu 15.10 (64 bits)
- Kernel: 4.2.0-30-generic
- Disk scheduler: Deadline (default)
- Filesystem: encrypted LVM with Btrfs
I have found many people who have solved similar problems by changing from the CFQ scheduler to Deadline, but Deadline is the default on the Ubuntu kernel. And I already had problems with the supposedly fast BFQ disk scheduler with no encryption.