Re: in defensive of zone_reclaim_mode on linux

Hi,

On 2015-09-04 15:37:47 -0700, Ben Chobot wrote:
> So our load would hover under 10 most of the time, then spike to over 100 for a minute or two. Connections would get refused, the system would freeze up... and then everything would go back to normal. The solution? Turning on zone_reclaim_mode.
>
> It appears that connection churn is far more manageable to Linux with zone_reclaim_mode enabled. I suspect that our dearth of large, complex queries helps us out as well. Regardless, our systems no longer desperately seek free memory when many idle backends wake up while others are getting torn down and and replaced. Babies and puppies rejoice.
>
> Our situation might not apply to you. But if it does, give zone_reclaim_mode a chance. It's not (always) as bad as others have made it out to be.

To me that sounds like the negative impact of transparent hugepages
being mitigated to some degree by zone reclaim mode (which'll avoid some
cross-node transfers).

Greetings,

Andres Freund