Subject: Re: Is pg_basebackup Performance Limited by Files Page Cache?

From: Alexandru Lazarev <[email-masked]>
Date: Wed, 26 Mar 2025 23:17:00 +0200

In my case culprit is Linux Kernel (Oracle Linux 9.2: RHCK 5.14 - issue
exists, after switched to UEK 5.15 Kernel issue disappears).
I did various tests with PG container and rsync too and even out of
container (launched rsync into a CgroupV2).

So now I guess it is a question to Linux Kernel communities in my case.
More details: https://www.reddit.com/r/linuxquestions/s/ADScolw76C

AlexL

On Wed, Mar 26, 2025, 21:16 kaido vaikla <[email-masked]> wrote:

> Hi,
> Did you get any feedback?
> I have suspected something similar.
>
> br
> Kaido
>

---

From: Alexandru Lazarev <[email-masked]>
Date: Wed, 9 Apr 2025 14:20:22 +0300

I'll answer my own question here:
Looks like it is a bug in Oracle Linux (OL) 9.2 RHCK Kernel
"kernel-5.14.0-284.11.1" (see table:
https://docs.oracle.com/en/operating-systems/oracle-linux/9/boot/oracle_linux9_kernel_version_matrix.html)

Switching to UEK Kernel of the same OL version (9.2) fixed the issue,
but UEK is not supported by some SW (e.g. Vertica DB), so that I've
tried RHCK Kernels update: only Kernel and dependencies from OL9.4
(kernel-5.14.0-427) and OL9.5 (kernel-5.14.0-503.11.1) - both fixed
the issue, with remark: RHCK update using one from OL9.5 is suspected
to have some HW compatibility issues (under investigation).
Some more details discussed here: Performance Degradation with rsync
in container or cgroupv2 with MEM limit on Oracle Linux 9.2 (RHCK 5.14
vs. UEK 5.15)

On Wed, Mar 26, 2025 at 11:17 PM Alexandru Lazarev
<[email-masked]> wrote:
>
> In my case culprit is Linux Kernel (Oracle Linux 9.2: RHCK 5.14 - issue exists, after switched to UEK 5.15 Kernel issue disappears).
> I did various tests with PG container and rsync too and even out of container (launched rsync into a CgroupV2).
>