Compression Policy

[Nigel Peck]

I am looking at how best to set up compression on my setup, that is a 
Varnish server handing out cached content from a separate back-end 
server. In his notes on the subject, Poul-Henning says that there is no 
need to store both a gzipped and an un-gzipped copy of requests in the 
cache, since Varnish can gunzip on the fly.

https://varnish-cache.org/docs/4.1/phk/gzip.html

My question is, wouldn't it be quicker to have both a gzipped and 
ungzipped copy stored in memory, so that this does not need to be 
changed on the fly? Or is the time taken to ungzip so negligible as to 
make this unnecessary?

Thanks
Nigel