Re: [PATCH v2 1/6] crypto: optimize algorithm registration when self-tests disabled

[Eric Biggers <ebiggers@kernel.org>]

On Thu, Nov 10, 2022 at 12:13:41AM -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.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  crypto/algapi.c | 151 ++++++++++++++++++++++++++----------------------
>  1 file changed, 82 insertions(+), 69 deletions(-)

FYI, I realized that this patch breaks CRYPTO_MSG_ALG_LOADED (it isn't always
sent now).  So I'll have to send a new version at least for that.

- Eric