[petsc-users] Memory usage

[Mark Adams]

On Fri, Oct 29, 2021 at 4:40 AM Karthikeyan Chockalingam - STFC UKRI <
karthikeyan.chockalingam at stfc.ac.uk> wrote:

> Hello,
>
>
>
> I used the flags  -memory_view -malloc_log   to ran a problem on the same
> size on 32 cores and 64 cores.
>
>
>
> I understand what is total, max and min memory usage of the problem is.
>

Total is the sum of all 32/62 processes. Max is, as it says "Maximum (over
computational time)"


> However I don’t understand the difference between Maximum and Current
> process memory?
>
>
>

Current memory usage does not include some earlier high water mark in
memory usage.


> I also curious to understand why the memory usage is different on 32 cores
> (1 node, 2 sockets with 16 cores/socket) and 64 cores (2 nodes) for a
> problem of the same size?
>

There is some data and metadata that is stored redundantly on each process.


>
>
> On 32 core:
>
>
>
> Summary of Memory Usage in PETSc
>
> Maximum (over computational time) process memory:        total 7.5014e+10
> max 2.6396e+09 min 2.0659e+09
>
> Current process memory:
>                       total 3.2583e+10 max 1.3562e+09 min 8.3587e+08
>
>
>
> On 64 core:
>
>
>
> Summary of Memory Usage in PETSc
>
> Maximum (over computational time) process memory:        total 7.9337e+10
> max 1.5433e+09 min 1.0319e+09
>
> Current process memory:
>                       total 6.4491e+10 max 1.2090e+09 min 8.4000e+08
>
>
>
> Kind regards,
>
> Karthik.
>
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