gpgsm: Use a cache to speed up parent certificate lookup.
* sm/gpgsm.h (COMPAT_NO_CHAIN_CACHE): New. (struct cert_cache_item_s, cert_cache_item_t): New. (struct server_control_s): Add parent_cert_cache. * sm/gpgsm.c (compatibility_flags): Add "no-chain-cache". (parent_cache_stats): New. (gpgsm_exit): Print the stats with --debug=memstat. (gpgsm_deinit_default_ctrl): Release the cache. * sm/certchain.c (gpgsm_walk_cert_chain): Cache the certificates. (do_validate_chain): Ditto.
This gives another boost of 30% (from 6.5 to 4.0 seconds in the test
environment with ~1000 certs). do_validate_chain actually brings us
the speedup becuase the gpgsm_walk_cert_chain is not used during a key
listing. For the latter we actually cache all certificates because
that was easier.
- GnuPG-bug-id: T7308