I see that Python 3's implementation of sha256 is x2 faster than Rust's one from sha2 crate. And consequences are so big that this makes great argument for not using Rust at all (see reasons below).

Tests done in Debian Linux sid in docker on Librem Purism. x86_64-unknown-linux-gnu. rustc 1.72.0-nightly. Here is sh.py3:

#!/usr/bin/env python3

import io, hashlib

with open("/home/user/dedup-bench/sto/00", "rb") as f:
    digest = hashlib.file_digest(f, "sha256")

print(digest.hexdigest())

/home/user/dedup-bench/sto/00 is raw disk image. Size is 2147483648 bytes.

Here is Cargo.toml:

[package]
name = "s"
version = "0.1.0"
edition = "2021"

[dependencies]
hex = "0.4.3"
#sha2 = { version = "0.10.7", features = ["asm"] }
sha2 = { version = "0.10.7", features = [] }

main.rs:

fn main() {
    use sha2::Digest;
    use std::io::Read;
    let mut hasher = sha2::Sha256::new();
    let mut buf = vec![];
    std::fs::File::open("/home/user/dedup-bench/sto/00").unwrap().read_to_end(&mut buf).unwrap();
    hasher.update(&buf);
    println!("{}", hex::encode(hasher.finalize()));
}

Here are results:

<[sid]>root@377503f894a2:~/s# time -p python3 ~/sh.py3
97856e0ae559f80dc3cde36cc23a3e37ae3ce2b92eed22ae5d7ec55e36c4401d
real 5.83
user 5.41
sys 0.41
<[sid]>root@377503f894a2:~/s# time -p python3 ~/sh.py3
97856e0ae559f80dc3cde36cc23a3e37ae3ce2b92eed22ae5d7ec55e36c4401d
real 5.79
user 5.44
sys 0.35
<[sid]>root@377503f894a2:~/s# time -p cargo run --release
    Finished release [optimized] target(s) in 0.01s
     Running `target/release/s`
97856e0ae559f80dc3cde36cc23a3e37ae3ce2b92eed22ae5d7ec55e36c4401d
real 13.28
user 12.24
sys 1.03
<[sid]>root@377503f894a2:~/s# time -p cargo run --release
    Finished release [optimized] target(s) in 0.01s
     Running `target/release/s`
97856e0ae559f80dc3cde36cc23a3e37ae3ce2b92eed22ae5d7ec55e36c4401d
real 13.25
user 12.22
sys 1.03

Results with asm are slightly better, but still way worse than Python's:

<[sid]>root@377503f894a2:~/s# time -p cargo run --release
   Compiling s v0.1.0 (/root/s)
    Finished release [optimized] target(s) in 0.27s
     Running `target/release/s`
97856e0ae559f80dc3cde36cc23a3e37ae3ce2b92eed22ae5d7ec55e36c4401d
real 11.33
user 10.29
sys 1.10
<[sid]>root@377503f894a2:~/s# time -p cargo run --release
    Finished release [optimized] target(s) in 0.01s
     Running `target/release/s`
97856e0ae559f80dc3cde36cc23a3e37ae3ce2b92eed22ae5d7ec55e36c4401d
real 11.06
user 10.03
sys 1.03

Here is /proc/cpuinfo:

Details

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 61
model name      : Intel(R) Core(TM) i7-5557U CPU @ 3.10GHz
stepping        : 4
microcode       : 0x2f
cpu MHz         : 3061.085
cache size      : 4096 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 20
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid rdseed adx smap intel_pt xsaveopt dtherm arat pln pts md_clear flush_l1d
vmx flags       : vnmi preemption_timer invvpid ept_x_only ept_ad ept_1gb flexpriority tsc_offset vtpr mtf vapic ept vpid unrestricted_guest ple
bugs            : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit srbds mmio_unknown
bogomips        : 6185.31
clflush size    : 64
cache_alignment : 64
address sizes   : 39 bits physical, 48 bits virtual
power management:

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 6
model           : 61
model name      : Intel(R) Core(TM) i7-5557U CPU @ 3.10GHz
stepping        : 4
microcode       : 0x2f
cpu MHz         : 3092.733
cache size      : 4096 KB
physical id     : 0
siblings        : 2
core id         : 1
cpu cores       : 2
apicid          : 2
initial apicid  : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 20
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid rdseed adx smap intel_pt xsaveopt dtherm arat pln pts md_clear flush_l1d
vmx flags       : vnmi preemption_timer invvpid ept_x_only ept_ad ept_1gb flexpriority tsc_offset vtpr mtf vapic ept vpid unrestricted_guest ple
bugs            : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit srbds mmio_unknown
bogomips        : 6185.31
clflush size    : 64
cache_alignment : 64
address sizes   : 39 bits physical, 48 bits virtual
power management:

Both crate cpufeatures and is_x86_feature_detected!("sha") report that my CPU does not have sha extension.

So sha extension is not supported. And Python beats Rust here. I think this my report belongs to this issue.

I discovered this problem when I compared borg performance and my own simple Rust program: borgbackup/borg#7674 . Hash computing is main reason of slowness of my Rust implementation. It is impossible to beat borg speed in sha256 mode for Rust. So, if for some reason I have need to create borg replacement with sha256, it will be simply impossible (with current state of ecosystem) to create proper alternative in Rust. So currently bad sha2 performance is valid reason to not chose Rust at all. So, please, raise importance of this issue

sha2: explore addition of SSE and AVX2 backends for SHA-256 #327

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