New: libopenssl (static): huge drop in performance in newer versions of buildroot

https://bugs.busybox.net/show_bug.cgi?id=13751

Bug ID: 13751
Summary: libopenssl (static): huge drop in performance in newer
versions of buildroot
Product: buildroot
Version: 2021.02.1
Hardware: All
OS: Linux
Status: NEW
Severity: normal
Priority: P5
Component: Other
Assignee: unassigned at buildroot.uclibc.org
Reporter: maksis33 at gmail.com
CC: buildroot at uclibc.org
Target Milestone: ---

I've done some benchmarking with different TLS 1.3 ciphers with an Intel Celeron N3150 CPU that has support for the AES-NI instruction set. I used static builds of AirDC++ Web Client (http://airdcpp-web.github.io) that were built with different versions of buildroot. Target architecture is x86_64 (nocona). Transfer speeds are limited by the CPU (one core is maxed out).

Encrypted download speeds (Buildroot 2021.02.1):

TLS_AES_128_GCM_SHA256: 27 MB/s
TLS_AES_256_GCM_SHA384: 24 MB/s
TLS_CHACHA20_POLY1305_SHA256: 41 MB/s

Encrypted download speeds (Buildroot 2019.02):

TLS_AES_128_GCM_SHA256: 62 MB/s
TLS_AES_256_GCM_SHA384: 59 MB/s
TLS_CHACHA20_POLY1305_SHA256: 54 MB/s

Note that those are actual network file transfers with additional overhead, so the plain decrypt speed difference should be much bigger than that ("openssl speed -evp aes-128-cbc" is about 5x faster than "openssl speed aes-128-cbc" on the same system).

I'd assume that the issue has something to do with
http://lists.busybox.net/pipermail/buildroot/2019-October/263030.html as the OpenSSL target arch is "gcc no-asm" in Buildroot 2021.02.1 while 2019.02 targets "linux-x86_64" and also has various *_ASM flags present in the Makefile. I also confirmed with objdump that the binary built with 2021.02.1 is missing all references to aesenc/aesdec/other AES-NI instructions while those instructions are present in the binary built with 2019.02.

I read
https://github.com/openssl/openssl/commit/87bea6550ae0dda7c40937cff2e86cc2b0b09491
and https://github.com/openssl/openssl/issues/9839 but I don't fully understand why the target architecture was changed. I'd say that ASM support is a must for applications similar to AirDC++.

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https://bugs.busybox.net/show_bug.cgi?id=13751

--- Comment #1 from Arnout Vandecappelle <[email protected]> --- (In reply to maksis33 from comment #0)

The culprit is actually the following commit:

commit 8c2c959b028d44f5518d4445f864aedae3d90406

Author: Fabrice Fontaine <[email protected]>
Date:   Fri May 31 15:39:28 2019

package/libopenssl: fix static build

no-dso option has been removed with

https://github.com/openssl/openssl/commit/31b6ed76dfd53529b74e79830c81372d0b756929

To fix this error, use "gcc" target in static builds. This target is very minimalistic, we need to manually pass -lpthread and -DOPENSSL_THREADS however we can also remove libdl workarounds

Fixes:
-
http://autobuild.buildroot.org/results/96d6b89d20980e8f7fa450b832474a81d492b315

The problem is that in a static build, you don't have shared libraries so also no DSO (the shared library provided by the kernel).

The upstream commit also adds a preprocessor symbol DSO_NONE (which is not set by anything). So you could try reverting buildroot commit 8c2c959b028d44f5518d4445f864aedae3d90406 and add -DDSO_NONE to LIBOPENSSL_CFLAGS.

Of course the revert is not entirely trivial, because the code was refactored and has moved to Config.in...

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--- Comment #2 from Fabrice Fontaine <[email protected]> ---
Could you try
https://patchwork.ozlabs.org/project/buildroot/patch/20210425133845.2459496-1-fontaine.fabrice at gmail.com/?

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--- Comment #3 from maksis33 at gmail.com ---
I tested the patch and it seems to fix the issue. Performance is now similar to Buildroot 2019.02.

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Yann E. MORIN <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------

         Resolution|---                         |FIXED
                 CC|                            |yann.morin.1998 at free.fr
             Status|NEW                         |RESOLVED

--- Comment #4 from Yann E. MORIN <[email protected]> --- Hello,

Thanks for your report. We believe this has now been fixed with commit 67d19f6014 (package/libopenssl: fix performance issue in static build) as provided by Fabrice.

Thanks!

Regards,
Yann E. MORIN.

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--- Comment #5 from Peter Korsgaard <[email protected]> ---
Also backported to 2021.02.x and will be part of the upcoming 2021.02.2 release

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