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
PG Doc comments form <noreply@postgresql.org> 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
On Wed, Oct 6, 2021 at 3:48 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
PG Doc comments form <noreply@postgresql.org> 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:
00007f2932eb6000 145360K rw-s- zero (deleted)
If you are already using huge pages, it doesn't match anything,
because the relevant line looks like:
00007f6814e00000 145408K rw-s- anon_hugepage (deleted)
Thanks Thomas. Looks like I misread that.
On Wednesday, 6 October, 2021, 04:56:42 am IST, Thomas Munro <thomas.munro@gmail.com> wrote:
On Wed, Oct 6, 2021 at 3:48 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
PG Doc comments form <noreply@postgresql.org> 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:
00007f2932eb6000 145360K rw-s- zero (deleted)
If you are already using huge pages, it doesn't match anything,
because the relevant line looks like:
00007f6814e00000 145408K rw-s- anon_hugepage (deleted)