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#### **--cpu-shares**, **-c**=*shares*
CPU shares (relative weight).
By default, all containers get the same proportion of CPU cycles. This
proportion can be modified by changing the container's CPU share weighting
relative to the combined weight of all the running containers.
Default weight is **1024**.
The proportion will only apply when CPU-intensive processes are running.
When tasks in one container are idle, other containers can use the
left-over CPU time. The actual amount of CPU time will vary depending on
the number of containers running on the system.
For example, consider three containers, one has a cpu-share of 1024 and
two others have a cpu-share setting of 512. When processes in all three
containers attempt to use 100% of CPU, the first container would receive
50% of the total CPU time. If a fourth container is added with a cpu-share
of 1024, the first container only gets 33% of the CPU. The remaining containers
receive 16.5%, 16.5% and 33% of the CPU.
On a multi-core system, the shares of CPU time are distributed over all CPU
cores. Even if a container is limited to less than 100% of CPU time, it can
use 100% of each individual CPU core.
For example, consider a system with more than three cores.
If the container _C0_ is started with **--cpu-shares=512** running one process,
and another container _C1_ with **--cpu-shares=1024** running two processes,
this can result in the following division of CPU shares:
| PID | container | CPU | CPU share |
| ---- | ----------- | ------- | ------------ |
| 100 | C0 | 0 | 100% of CPU0 |
| 101 | C1 | 1 | 100% of CPU1 |
| 102 | C1 | 2 | 100% of CPU2 |
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