Re: git: 32a2fed6e71f - stable/13 - openssl: Fix detection of ARMv7 and ARM64 CPU features
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Date: Thu, 25 Nov 2021 16:54:06 UTC
On 11/25/2021 10:31 AM, Helge Oldach wrote: > Allan Jude wrote on Thu, 25 Nov 2021 16:09:25 +0100 (CET): >> On 11/25/2021 2:38 AM, Helge Oldach wrote: >>> hmo@p48 ~ $ for f in 0 1 2 3 8 16 32 64 128 ; do echo -n $f:; env OPENSSL_armcap=$f openssl speed -evp aes-256-gcm 2>&1 | tail -1 | cut -wf7; done >>> 0:42295.15k >>> 1:23891.19k >>> 2:42208.57k >>> 3:23970.56k >>> 8:42354.98k >>> 16:42199.06k >>> 32:size >>> Illegal instruction (core dumped) >>> 64:42322.42k >>> 128:42275.00k >>> hmo@p48 ~ $ >>> >>> So I guess HWCAP_FP is the culprit? Maybe related to hard/soft floating >>> point math which indeed is kind of special on the Pi? >> >> So yeah, the issue seems to be that floating point on the RPi4 is slower >> than not, but now openssl (properly) detects that the CPU advertises >> support for it. >> >> As seen elsewhere in the thread, most other ARM platforms get a very >> significant speed boost. > > So can we disable FP within OpenSSL for the RPi by default? This commit > basically introduced a regression for this platform and I think that > should be fixed. > > Or it the root cause a suboptimal FP implementation that is not adequate > for the RPi? > > Kind regards > Helge > The root cause is that the RPi4 advertises support for FP, but its FP is slow. I don't know that there is an easy way to detect the RPi4 specifically. You might be able to just disable the FP bit by setting OPENSSL_armcap=~1 globally, or maybe via openssl.conf? -- Allan Jude