On 11.04.2017, Paolo Valente wrote: > new patch series, addressing (both) issues raised by Bart [1]. I'm doing a lot of automatic video transcoding in order to get my collection of homemade videos down to an acceptable size (mainly landscapes and boats all over the Norwegian west coast, taken with an old cam that only produces uncompressed files). This process involves heavy permanent writing to disk, often over a period of 10 min and more. When this happens, the whole system is kind of unresponsive. I'm running Fedora 25, but with a self-customised kernel that is fully low-latency, and the machine is a quadcore Intel Xeon which should have enough power (Intel(R) Xeon(R) CPU E3-1241 v3 @ 3.50GHz). Using plain blk-mq, the system is very sluggish when there is heavy disk writing, and it can take up to several minutes (up to the point where the disk writing actually finishes) to start programs like gimp or Libreoffice. In fact, when I click on the "applications" button within XFCE, it can take a long time before the window even opens. I played with deadline-mq too, and the situation remains the same unless I do some heavy tuning like this: echo "mq-deadline" > /sys/block/nvme0n1/queue/scheduler echo "1" > /sys/block/nvme0n1/queue/iosched/fifo_batch echo "4" > /sys/block/nvme0n1/queue/iosched/writes_starved echo "100" > /sys/block/nvme0n1/queue/iosched/read_expire echo "2000" > /sys/block/nvme0n1/queue/iosched/write_expire With deadline-mq tuned like this, overall responsiveness is a little bit better, but not nearly as good as when using bfq. With plain bfq, no tuning is needed. The system is no longer sluggish. Any program starts within seconds, and all is very much responsive. Max throughput isn't important to me, the nvme "harddisk" is fast enough that some MB/s more or less do not really matter. [root@chiara ~]# lspci -v | grep -i nvme 01:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller SM951/PM951 (rev 01) (prog-if 02 [NVM Express]) Kernel driver in use: nvme Kernel modules: nvme As an end-user with no relevant programming skills to be able to contribute, I would wish that developers would combine their forces and help Paolo to get bfq into the kernel and to make bfq even better. Thanks, Heinz
