Re: checkpoint process use too much memory

On 2020-Jul-20, jian xu wrote:

>       we are seeing this issue again, the checkpoint process is eating up all the memory,
> based on the htop, the checkpointer process has
> VIRT: 103G
> RES: 103G
> SHR: 4099M
> MEM%: 41%
> 
> I use ps_mem.py to check the process,
> https://github.com/pixelb/ps_mem
> =================================
>  Private  +   Shared  =  RAM used Program
> 
>  99.5 GiB +  37.5 MiB =  99.5 GiB postgres
> ---------------------------------
>                                            99.5 GiB
> =================================
> my pg version is 10.3 , shared_buffer size is 4GB. work_mem 64MB. there are about 120 connections on the db side.
mostof them are idle.
 
> does anyone have idea how to troubleshooting this kind of issue?

I see no reason for checkpointer to use that much memory.  Accounting
for the whole of shared_buffers is okay (as Laurenz explaijned), which
in other installations may account for several gigabytes of memory.  But
if shared_buffers is 4GB, then 99GB is clearly overboard.  I see no
explanation for checkpointer using 25x shared_buffers.

Maybe looking at /proc/<PID>/smaps would tell you where that memory is
going?  Have a look there are see if you can figure out some obviously
absurd entries.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
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