Performance : slowness during 'packing' time with Hermit CLI.

[mtb0x1]

I am opening this issue to discuss possible performance improvements that can be brought to Hermit CLI.

Measurements below are based on PR #23 : the throughput of hermit.com is not constant and degrades with medium to big inputs, the time required for packing increases with larger inputs. few data points below :

	Count Vowels	Ubuntu	Emacs
Pack time	795ms	1m33s	8m30s
Throughput	2.6Mb/s	1.7Mb/s	1.6Mb/s
.wasm size	2.1Mb	160Mb	853Mb
.com size	1.2Mb	63Mb	330Mb

*Wasm files of Ubuntu and Emacs were generated using container2wasm.

After few runs with verbose mode, a pattern emerged. The root cause of the slowness is the zipping of *.wasm in https://github.com/dylibso/hermit/blob/main/hermit-cli/crates/hermitfile-parser/src/main.rs#L181-L187.

A change of config as follow, results in a different performance results:
https://github.com/mtb0x1/hermit/blob/zip_stored/hermit-cli/crates/hermitfile-parser/src/main.rs#L198-L214

	Count Vowels	Ubuntu	Emacs
Pack time	39ms	0m1s30ms	0m7s80ms
Throughput	53Mb/s	123Mb/s	109Mb/s
.wasm size	2.1Mb	160Mb	853Mb
.com size	2.7M	161Mb	853Mb

A drastic change in performance that have a downside, the size of produced artifacts. but in the other hand, I don't think that users will expect any 'out of the box' binaries size reduction.

My suggestion would be to add options to Hermit cli to allow the user to choose a 'packing' strategy.
the strategy would be somehow similar to what classic compilers have already :

• Optimization for size : would allow a level of compression to be specified.
• Optimization for speed (use Stored instead of Deflated)

N.B :

• Modifications introduced have an impact on both hermit.com and artifacts produced by it. I would recommend separating this in 2 stages and avoid sharing same optimization strategy.
• Modifications introduced at the 'packing' step have an impact on runtime of artifacts. (faster boot of .com CLI, still slow but this would be a subject of another issue in the future.)

[G4Vi]

A packing strategy flag would be a great edition to the cli! Longer term we're interesting in improving the performance of hermit (possibly running the wasm with a JIT) so DEFLATE hopefully won't be an issue then.