| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Christoph Berg <myon(at)debian(dot)org> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)postgresql(dot)org>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: pgsql: Introduce pg_shmem_allocations_numa view |
| Date: | 2025-06-23 15:14:54 |
| Message-ID: | g3mywoeo7jmh6rci7epx2ishowgz65q2j7ek3c5f3lxcmvuktg@ler2fsv4szmn |
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Hi,
On 2025-06-23 16:48:27 +0200, Christoph Berg wrote:
> Re: To Tomas Vondra
> > Why do we try to force the pages to be allocated at all? This is just
> > a monitoring function, it should not change the actual system state.
The problem is that the kernel function just gives bogus results for pages
that *are* present in memory but that have only touched in another process
that has mapped the same range of memory.
> One-time touching might also not be enough, what if the pages later
> get swapped out and the monitoring functions are called again?
I don't think that's a problem, the process still has a relevant page table
entry in that case.
Greetings,
Andres Freund
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