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From ezko <erez.ko...@harmonicinc.com>
Subject optimize ram_cache.size and ram disk size for live content
Date Tue, 05 Dec 2017 14:59:04 GMT
Hi.
I'm trying to optimize ATS reverse proxy configuration.
My origin is serving live HLS so all objects are short term lived. 

My typical HLS live channel has 4 profiles (0.2Mbit , 0.6 Mbit , 1.2Mbit and
2Mbit). 
The playlist has 15 segments , each 4 seconds in length. So the total memory
needed to cache one HLS channel is at worst (0.2+0.6+1.2+2) * 4 * 15 = 30
Mbytes + a few more bytes for the playlist (i'm using header_rewite plugin
with READ_RESPONSE_HDR_HOOK (thanks to Miles Libbey) to set the max-age for
the segments to 60 seconds , so hopefully ATS will evict old segments in
step with the playlist sliding window)

Anyway ideally I would like ATS to use RAM cache only , but i understand
that's currently not an option with ATS , so RAM disk is the best
alternative.

Should i use ATS cache ram (proxy.config.cache.ram_cache.size) , and if yes
what size should i set ? 
How does ATS prevent its own cache ram from being swapped to disk ?

For the cache file in storage.config , what type of ram disk should i use ?
tmpfs or ramfs ? 
tmpfs seems more controlled , but it could be swapped out.

thanks in advance.



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