What is freeable memory metric in AWS Elasticache

[Pradeep Reddy]

We launched a new Elasticache node (t2.micro) for testing, freeable memory dropped continuously from 580 MB to 50-100 MB over a period of 30 hours, now it has been constant more or less for the past 2 weeks. Traffic to redis is always same.

Is the freeable memory = memory used by OS for caching purposes ?
Or freeable memory = memory available after OS has used all it can ?

Is it a good idea to monitor this metric for making scaling up/out decisions?

Redis memory info

used_memory:7707152
used_memory_human:7.35M
used_memory_rss:161832960
used_memory_peak:176503816
used_memory_peak_human:168.33M
used_memory_lua:35840
mem_fragmentation_ratio:21.00
mem_allocator:jemalloc-3.6.0

[Paweł Furmaniak]

I have very similar situation and I am also looking for explanation.

[Colin Vipurs]

It would appear to be memory used by the OS cache as described here: https://forums.aws.amazon.com/thread.jspa?threadID=141154

"FreeableMemory is the memory that's being consumed by OS cache, and it will be given back when needed and nothing to worry about."

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Maybe she awoke to see the roommate's boyfriend swinging from the chandelier wearing a boar's head.

Something which you, I, and everyone else would call "Tuesday", of course.

[Paweł Furmaniak]

Based on this definition, there can be following reasons behind FreeableMemory going down:

• the memory is actually being freed
• total available memory is decreasing 

I hope it's the first one.