Controlling syft's parallelism & reduce memory usage

[tomerse-sg]

What would you like to be added:
hi, is their a way to control Syft parallelism (number of workers)?
moreover, do you have any suggestions how can I reduce memory consumption via configuration (I want to create image SBOM)?

Why is this needed:
I want to optimize the memory usage of syft according to my needs

Additional context:

[wagoodman]

There is a configuration option for this (which looks to be accidentally undocumented): SYFT_PARALLELISM env var (default value is 1)

syft/internal/config/application.go

Line 67 in e2f7bef

Parallelism int `yaml:"parallelism" json:"parallelism" mapstructure:"parallelism"` // the number of catalog workers to run in parallel

introduced in PR: #1355

[tgerla]

Hopefully the "parallelism" option does what you need here. We'll go ahead and close this issue, but please let us know if you need anything else!