CPU Cores and Redis

[Kashyap Mhaisekar]

Hi,

Our redis servers are showing high CPU%.

I was wondering if single threaded model of CPU means that the thread is always bound to 1 CPU?

The box has 4 cores but we see only one CPU has 80% CPU while other 3 have hardly 10%. There are no other tasks running on the box.

Could you please let me know?

Thanks

Kashyap

[Javier Guerra Giraldez]

On Thu, Jul 30, 2015 at 5:08 PM, Kashyap Mhaisekar <kash...@gmail.com> wrote:
> I was wondering if single threaded model of CPU means that the thread is
> always bound to 1 CPU?

yes

--
Javier

[Josiah Carlson]

A small clarification: you should only have 1 active core with Redis unless/until it forks for snapshotting/aof rewriting. But it doesn't bind itself to a specific CPU, and may migrate from core to core, but only one core would be active at any one time.

 - Josiah

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[Kashyap Mhaisekar]

Thanks Josh. There is no property that determines if cores need to switch right?

Thanks
Kashyap

[Josiah Carlson]

On Thu, Jul 30, 2015 at 10:00 PM, Kashyap Mhaisekar <kash...@gmail.com> wrote:

Thanks Josh.

You're missing 2 letters in there ;) 

There is no property that determines if cores need to switch right?

Redis doesn't do anything explicit or implicit to choose the core that it runs on. That is all controlled by the kernel scheduler, which you can override using the 'taskset' command in Linux, or similar functionality available on other OSes.

 - Josiah

[Kashyap Mhaisekar]

Sorry and thanks again Josiah :)