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The tuned-profiles-cloudlinux package brings a range of kernel under-the-hood tunings to address high LA, iowait issues what were detected earlier on particular users deploys. The package also encloses OOM adjustments to prioritize the elimination of overrun php, lsphp, Phusion Passenger workers processes over other processes (e.g. ssh, a cron job).


There are three profiles provided by CloudLinux:


# tuned-adm list | grep cloudlinux

- cloudlinux-default          - Default CloudLinux tuned profile

- cloudlinux-dummy            - Empty CloudLinux tuned profile

- cloudlinux-vz               - Empty CloudLinux tuned profile


cloudlinux-dummy and cloudlinux-vz are used for internal needs or when Virtuozzo/OpenVZ detected and actually do nothing.


cloudlinux-default is one to be used, it actually does the following:


1. Switches CPU power consumption mode to the maximum. CPU operates at maximum performance at the maximum clock rate:





Note. If standard software CPU governors are used.


2. Applies the following kernel options:


vm.force_scan_thresh=100 - Improves kernel memory clean-up in case of big number of running LVE.


UBC parameters set the limits for the containers:


ubc.dirty_ratio=100 - Defines maximum RAM percentage for dirty memory pages.

ubc.dirty_background_ratio=75 - Defines RAM percentage when to allow writing dirty pages on the disk.


3. [CloudLinux 7 only] Detects used disk types and changes elevator to 'deadline' for HDD and to 'noop' for SSD in /sys/block/[blockname]/queue/scheduler .


Note. The script uses /sys/block/[blockname]/queue/rotational flag, some RAID controllers can not set it properly. For example, SSD used for RAID but rotational is set to 1 by RAID driver. As a workaround add the following to /etc/rc.d/rc.local to make it applied on boot:


echo "noop" > /sys/block/[blockname]/queue/scheduler

echo "0" > /sys/block/[blockname]/queue/rotational


Where [blockname] is used device name, like sda/sdb.


And make it executable:


chmod +x /etc/rc.d/rc.local


4. [CloudLinux 7 only] The profile sets I/O scheduler. For the normal discs the Deadline Scheduler is set to improve IO performance and decrease IO latency, for SSD - noop.

When configuring scheduler I/O queue is changed and set to the value 1024 which improves overall I/O subsystem performance by caching IO requests in memory.


5. Disables transparent HugePage.


6. Provides adjustment group file for OOM-Killer to kill overrun php, lsphp and Phusion Passenger workers first.


To install:


yum install tuned-profiles-cloudlinux


To start using a profile:


tuned-adm profile cloudlinux-default


To stop using a profile:


tuned-adm off