[CentOS] Measuring memory bandwidth utilization

[Oscar Osta Pueyo]

Hello,
Try to install collectd and check the metrics for ram.

Best regards,
El dia 03/02/2016 2:51 a. m., "John R Pierce" <pierce at hogranch.com> va
escriure:

> On 2/2/2016 5:34 PM, Benjamin Smith wrote:
>
>> I'd like to know what the cause of a particular DB server's slowdown
>> might be.
>> We've ruled out IOPs for the disks (~ 20%) and raw CPU load (top shows
>> perhaps
>> 1/2 of cores busy, but the system slows to a crawl.
>>
>> We're suspecting that we're simply running out of memory bandwidth but
>> have no
>> way to confirm this suspicion. Is there a way to test for this? Think:
>> iostat
>> but for memory bandwidth instead of disk IO.
>>
>
> memory bandwidth would show up as CPU busy, there's no distinction.
>
> 50% of your cores 100% busy, how many cores and how many waiting database
> tasks are there?  typically with most database servers, one user connection
> == one core at a time.   so if you have 16 cores, and only 8 busy/active
> database connections, that will tie up those 8 cores and leave the other 8
> free.    now the 8 processes will probably get bounced around between the
> cores, so it could end up looking like all 16 cores are 50% busy averaged
> over some sample rate, but thats the same net difference..
>
>
>
> --
> john r pierce, recycling bits in santa cruz
>
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