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Slow disk access and overall speed issues in newer ubuntu and linux mint

April 10, 2017 Leave a comment

I have the subjective feeling that the newer versions of ubuntu and its derivatives including linux mint has slowed up a bit compared to pre unity ubuntus(11.04) or linux mint 17. I had been looking for the reason for some time. This probably won’t apply to you unless you are using a slow ‘hard disk’. The symptom is that subjectively the disk access latencies are larger (eg. applications take longer to start).

Linux has a software component called the IO scheduler. This takes care of scheduling requests to the permanent storage devices. There are a few choices for the algorithm to be used for this purpose. The choices and current selection can be seen by issuing

cat /sys/block/sda/queue/scheduler

(For me the sda is the drive containing all linux partitions. It may change for you ie. sda, sdb, sdc.. or hda, hdb, hdc…)

The default in modern ubuntu and linux mint is the ‘deadline‘ scheduler; probably a decision based on benchmark performance results on modern hardware. I changed this to ‘cfq‘, and subjectively the system became a lot more responsive. You can temporarily tryout the setting by writing the new scheduler name to the above file using command

sudo sh -c 'echo cfq > /sys/block/sda/queue/scheduler'

If you find think system responsiveness is better than before, you can make the changes permanent by writing following settings to /etc/default/grub and running update-grub2

sudo vim /etc/default/grub

Type the setting

GRUB_CMDLINE_LINUX="elevator=cfq"

Exit editor.

update-grub2

From next reboot onwards the setting should now takeplace at boot itself.