work_mem value can be bad

[roger-rainey]

The code that calculates work_mem can produce a value that is below the minimum threshold of 64kB. This will prevent timescale/postgress from starting. I have experienced this issue deploying to a k8s node w/ 32 Cores and 120GB Ram. The output from timescale-tune was 41kB which causes postgres to fail to start.

[RobAtticus]

Yikes, that's no good. Did you set any other flags I should know about?

Will definitely look to push a fix ASAP

[RobAtticus]

I ask because when I try

timescaledb-tune --memory=120GB --cpus=32

I get this for memory settings

Recommendations based on 120.00 GB of available memory and 32 CPUs for PostgreSQL 11
shared_buffers = 30GB
effective_cache_size = 90GB
maintenance_work_mem = 2047MB
work_mem = 19660kB

So I wonder how it ended with 64KB

EDIT: Fixed memory flag

[roger-rainey]

No flags were added and it gave me a value of 41k so it would not run

…

On Mon, Mar 4, 2019, 6:50 PM RobAtticus ***@***.***> wrote: I ask because when I try timescaledb-tune --memory=32GB --cpus=32 I get this for memory settings Recommendations based on 120.00 GB of available memory and 32 CPUs for PostgreSQL 11 shared_buffers = 30GB effective_cache_size = 90GB maintenance_work_mem = 2047MB work_mem = 19660kB So I wonder how it ended with 64KB — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#38 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AhMe_CRj85Gm5jUP3J2Xk2csaVW_Doerks5vTdttgaJpZM4bdfAH> .

[RobAtticus]

Happy to correct the issue with it returning invalid values, but I am a bit worried that is is misreading your settings since it should not be giving 41KB for the given parameters (120GB RAM, 32 CPUs).

It would be useful if you could run the following commands from inside the container:

cat /sys/fs/cgroup/memory/memory.limit_in_bytes

and

free -m | grep 'Mem' | awk '{print $2}'

Thanks for the bug report

[roger-rainey]

Here are the results of the commands you sent. Although this machine has a lot of resources, GKE probably slices it differently which produces those results. bash-4.4$ cat /sys/fs/cgroup/memory/memory.limit_in_bytes 268435456 bash-4.4$ free -m | grep 'Mem' | awk '{print $2}' 120873

…

On Tue, Mar 5, 2019 at 8:52 AM RobAtticus ***@***.***> wrote: Closed #38 <#38> via #39 <#39>. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#38 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AhMe_EzwcakF03OfZDQ9-dBKGOOgcNYWks5vTqDPgaJpZM4bdfAH> .

[RobAtticus]

This got closed by the merge but there seems to be another problem at play here.

Specifically, 268435456 is only ~268MB, so your settings are based off that rather than the 120GB actually available on the machine. Do you have any insight as to why the machine would be giving that as the limit?

[RobAtticus]

bump @roger-rainey

[roger-rainey]

The memory number was coming from kubernetes request memory which is not the memory limit.

…

On Mon, Mar 11, 2019 at 2:43 PM RobAtticus ***@***.***> wrote: bump @roger-rainey <https://github.com/roger-rainey> — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#38 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AhMe_NZk3mdQPpyLbCUSJnUh-n0QnRXoks5vVs3ygaJpZM4bdfAH> .

[LeeHampton]

@roger-rainey That's intriguing. The cgroups memory.limit_in_bytes should refer to the maximum memory allocated to the container, not the minimum requested. I could see it being possible that the two would match up if the node the container is scheduled on only has request_memory available, but with such a specific number that seems kind of weird.

Would you mind posting your k8s configuration for this pod, and any other information you have about resource utilization on the node your pod is on?

If it seems like there's still more than request_memory available, I might have to do a deeper dive on how the cgroups memory limits get set when request settings are specified in k8s.

[RobAtticus]

One other useful bit of info might be the output of

cat /sys/fs/cgroup/memory/memory.stat

[RobAtticus]

@roger-rainey Did you have any follow up on this re: @LeeHampton 's comment?