f10dc56c64
As it turns out, checking the TIF_NEED_RESCHED flag after each
iteration results in a significant performance regression (~10%)
when running fast algorithms (i.e., ones that use special instructions
and operate in the < 4 cycles per byte range) on in-order cores with
comparatively slow memory accesses such as the Cortex-A53.
Given the speed of these ciphers, and the fact that the page based
nature of the AEAD scatterwalk API guarantees that the core NEON
transform is never invoked with more than a single page's worth of
input, we can estimate the worst case duration of any resulting
scheduling blackout: on a 1 GHz Cortex-A53 running with 64k pages,
processing a page's worth of input at 4 cycles per byte results in
a delay of ~250 us, which is a reasonable upper bound.
So let's remove the yield checks from the fused AES-CCM and AES-GCM
routines entirely.
This reverts commit 7b67ae4d5ce8e2f912377f5fbccb95811a92097f and
partially reverts commit 7c50136a8aba8784f07fb66a950cc61a7f3d2ee3.
Fixes: 7c50136a8aba ("crypto: arm64/aes-ghash - yield NEON after every ...")
Fixes: 7b67ae4d5ce8 ("crypto: arm64/aes-ccm - yield NEON after every ...")
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.