On Wed, Nov 09, 2022 at 06:37:38PM -0800, Eric Biggers wrote:
From: Eric Biggers ebiggers@google.com
Currently, registering an algorithm with the crypto API always causes a notification to be posted to the "cryptomgr", which then creates a kthread to self-test the algorithm. However, if self-tests are disabled in the kconfig (as is the default option), then this kthread just notifies waiters that the algorithm has been tested, then exits.
This causes a significant amount of overhead, especially in the kthread creation and destruction, which is not necessary at all. For example, in a quick test I found that booting a "minimum" x86_64 kernel with all the crypto options enabled (except for the self-tests) takes about 400ms until PID 1 can start. Of that, a full 13ms is spent just doing this pointless dance, involving a kthread being created, run, and destroyed over 200 times. That's over 3% of the entire kernel start time.
Fix this by just skipping the creation of the test larval and the posting of the registration notification entirely, when self-tests are disabled. Also compile out the unnecessary code in algboss.c.
While this patch is an optimization and not a "fix" per se, I've marked it as for stable, due to the large improvement it can make to boot time.
Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers ebiggers@google.com
Unfortunately, this patch won't work because it breaks templates.
There should still be a solution that at least avoids having to spawn kthreads, though...
- Eric