Re: how to debug the postgres performance issue

On 09/14/2018 04:34 AM, 范国腾 wrote:
>
> Hi,
>
> We are doing the performance test in two nodes system(active/standby).
> Now we find that the disk IO is very high but the CPU is low.
>

On both nodes or just one (and if so, which one)?

If you incrementally increase the workload, starting from the quiescent
state, when do you see this happening?

> Is there any method or tool to help us debug to find which function
> makes this issue?
>
> We try to use the gprof but it does not help us. The result show the
> LWLockAssign（the shared buffer init）is called the most time. The other
> function is called no more that 33139. That seems no problem.
>
> Could you please  give any suggestion how to debug the high IO/low CPU
> issue?
>
> Thanks
>
> Steven
>
> ===================================
>
> no time accumulated
>
> %   cumulative   self              self total
>
>  time seconds   seconds    calls  Ts/call  Ts/call name
>
>   0.00 0.00     0.00  9240928     0.00     0.00 LWLockAssign
>
> 0.00      0.00     0.00    33139     0.00     0.00 ShmemAlloc
>
> 0.00      0.00     0.00    33084     0.00     0.00 seg_alloc
>
> ….
>

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