Correction to documentation at https://www.postgresql.org/docs/12/kernel-resources.html
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/12/kernel-resources.html
Description:
Hi.
On https://www.postgresql.org/docs/12/kernel-resources.html, the command to
calculate memory allocated to postgres is not correct. Following is the
command as shown in 18.4.5. Linux Huge Pages.
pmap 4170 | awk '/rw-s/ && /zero/ {print $2}', this command does not return
any results with correct pid. Probably /zero/ needs to be updated with
/anon_hugepage/
Thanks,
Sanjeev Adwal
Re: Correction to documentation at https://www.postgresql.org/docs/12/kernel-resources.html
PG Doc comments form writes:
> On https://www.postgresql.org/docs/12/kernel-resources.html, the command to
> calculate memory allocated to postgres is not correct. Following is the
> command as shown in 18.4.5. Linux Huge Pages.
> pmap 4170 | awk '/rw-s/ && /zero/ {print $2}', this command does not return
> any results with correct pid. Probably /zero/ needs to be updated with
> /anon_hugepage/
The example seems to work as-given for me (testing on a RHEL8 system).
It's of course not guaranteed to work on every flavor of Linux.
regards, tom lane
Re: Correction to documentation at https://www.postgresql.org/docs/12/kernel-resources.html
On Wed, Oct 6, 2021 at 3:48 AM Tom Lane wrote:
> PG Doc comments form writes:
> > On https://www.postgresql.org/docs/12/kernel-resources.html, the command to
> > calculate memory allocated to postgres is not correct. Following is the
> > command as shown in 18.4.5. Linux Huge Pages.
> > pmap 4170 | awk '/rw-s/ && /zero/ {print $2}', this command does not return
> > any results with correct pid. Probably /zero/ needs to be updated with
> > /anon_hugepage/
>
> The example seems to work as-given for me (testing on a RHEL8 system).
> It's of course not guaranteed to work on every flavor of Linux.
I think the pattern as given will show you the size if you are not
already using huge pages. For example, this line matches on my system
when I have /proc/sys/vm/nr_hugepages == 0:
7f2932eb6000 145360K rw-s- zero (deleted)
If you are already using huge pages, it doesn't match anything,
because the relevant line looks like:
7f6814e0 145408K rw-s- anon_hugepage (deleted)
