[Deepin-Kernel-SIG] [linux 6.18.y] [FROMLIST] genksyms: Support arm64 CRC32 hardware acceleration by opsiff · Pull Request #1759 · deepin-community/kernel

opsiff · 2026-05-25T06:48:01Z

maillist inclusion
category: performance

Use hardware 'crc32b' to build genksyms when support, it shows 2x speed up than crctab32 way.

Summary by Sourcery

Enhancements:

Detect arm64 CRC32 hardware support at runtime in genksyms and use hardware-accelerated CRC32 operations for symbol hashing when available.

sourcery-ai · 2026-05-25T06:48:07Z

Reviewer's Guide

Adds optional arm64 hardware-accelerated CRC32 support to genksyms, falling back to the existing table-based implementation when unavailable, and wires the detection into program startup.

Sequence diagram for arm64 CRC32 hardware acceleration in genksyms

sequenceDiagram
    participant Main
    participant crc32_check_hw
    participant partial_crc32
    participant partial_crc32_one
    participant crc32_hw_byte

    Main->>crc32_check_hw: crc32_check_hw()
    crc32_check_hw-->>Main: crc32_hw_available flag

    Main->>partial_crc32: partial_crc32(s, crc)
    alt [crc32_hw_available] on aarch64
        loop for each byte c in s
            partial_crc32->>crc32_hw_byte: crc32_hw_byte(c, crc)
            crc32_hw_byte-->>partial_crc32: updated crc
        end
    else [hardware unavailable or non aarch64]
        loop for each byte c in s
            partial_crc32->>partial_crc32_one: partial_crc32_one(c, crc)
            alt [crc32_hw_available] on aarch64
                partial_crc32_one->>crc32_hw_byte: crc32_hw_byte(c, crc)
                crc32_hw_byte-->>partial_crc32_one: updated crc
            else [crc32_hw_available false]
                partial_crc32_one-->>partial_crc32: crctab32-based crc
            end
        end
    end
    partial_crc32-->>Main: final crc

File-Level Changes

Change	Details	Files
Introduce runtime detection and use of arm64 CRC32 hardware instructions in genksyms while preserving the existing software CRC path as a fallback.	Add architecture-specific helpers to detect CRC32 hardware support via getauxval(HWCAP_CRC32) on aarch64 and track it in a global flag Implement an inline helper that performs a single-byte CRC32 update using the arm64 crc32b instruction when hardware is available Modify the byte-wise CRC routines to branch to the hardware-accelerated path on aarch64 using __builtin_expect hints, otherwise retain the crctab32-based implementation Initialize hardware detection early in main() so all subsequent CRC computations can leverage the hardware path when present	`scripts/genksyms/genksyms.c`

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sourcery-ai

Hey - I've left some high level feedback:

The inline assembly uses .arch_extension crc and crc32b directly, which may not be accepted by all aarch64 assemblers/toolchains; consider using compiler intrinsics (e.g., __builtin_aarch64_crc32b) or a feature macro check to improve portability.
Introducing a hard dependency on getauxval/HWCAP_CRC32 for the host tool may break builds on non-glibc or older libc environments; it would be safer to guard this with configure-time checks or provide a fallback path when getauxval is unavailable.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The inline assembly uses `.arch_extension crc` and `crc32b` directly, which may not be accepted by all aarch64 assemblers/toolchains; consider using compiler intrinsics (e.g., `__builtin_aarch64_crc32b`) or a feature macro check to improve portability.
- Introducing a hard dependency on `getauxval`/`HWCAP_CRC32` for the host tool may break builds on non-glibc or older libc environments; it would be safer to guard this with configure-time checks or provide a fallback path when `getauxval` is unavailable.

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Avenger-285714 · 2026-05-25T06:51:54Z

/approve

It looks linux-6.6.y needs this too.

BTW, do other arch have this?

deepin-ci-robot · 2026-05-25T06:52:22Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Avenger-285714, dongert

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Copilot

Pull request overview

This PR accelerates genksyms symbol hashing on arm64 hosts by detecting CRC32 CPU support at runtime and using the arm64 crc32b instruction when available, falling back to the existing table-based CRC32 otherwise.

Changes:

Add runtime detection for arm64 CRC32 hardware capability via getauxval(AT_HWCAP).
Implement a hardware-accelerated CRC32 byte update path using inline asm (crc32b) and use it in partial_crc32[_one].
Initialize the hardware capability check early in main().

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+#ifdef __aarch64__
+#include <sys/auxv.h>
+#include <asm/hwcap.h>
+
+static void crc32_check_hw(void)
+{
+	crc32_hw_available = (getauxval(AT_HWCAP) & HWCAP_CRC32) != 0;
+}


+#include <sys/auxv.h>
+#include <asm/hwcap.h>
+
+static void crc32_check_hw(void)
+{
+	crc32_hw_available = (getauxval(AT_HWCAP) & HWCAP_CRC32) != 0;
+}


maillist inclusion category: performance Use hardware 'crc32b' to build genksyms when support, it shows 2x speed up than crctab32 way. Signed-off-by: Wentao Guan <guanwentao@uniontech.com>

opsiff · 2026-05-25T08:39:32Z

/approve

It looks linux-6.6.y needs this too.

BTW, do other arch have this?

I will take it to 6.6,
LoongArch will have it.

Avenger-285714 · 2026-05-25T08:43:33Z

/approve
It looks linux-6.6.y needs this too.
BTW, do other arch have this?

I will take it to 6.6, LoongArch will have it.

If it's a multiarch feature, plz consider to do something such as making a light framework to make the code more pretty.

opsiff · 2026-05-25T10:00:10Z

If it's a multiarch feature, plz consider to do something such as making a light framework to make the code more pretty.

It has be included in the code now.

opsiff · 2026-05-25T10:01:09Z

/approve
It looks linux-6.6.y needs this too.
BTW, do other arch have this?

I will take it to 6.6, LoongArch will have it.

If it's a multiarch feature, plz consider to do something such as making a light framework to make the code more pretty.

for example:
just add crc32_check_hw() and crc32_hw_byte() for LoongArch version.

Avenger-285714 · 2026-05-25T11:20:53Z

It has be included in the code now.

#if defined(__aarch64__) xxx; #endif
It's ur framwork? ...

opsiff · 2026-05-25T11:23:42Z

It has be included in the code now.

#if defined(__aarch64__) xxx; #endif It's ur framwork? ...

It keep things simple, or why not use crc32 from <zlib.h>, which from zlib1g-dev and zlib1g.

Avenger-285714 · 2026-05-25T11:28:14Z

It keep things simple, or why not use crc32 from <zlib.h>, which from zlib1g-dev and zlib1g.

I'm not sure, maybe it's really better...

deepin-ci-robot requested review from Wenlp and shy129 May 25, 2026 06:48

Avenger-285714 requested review from Avenger-285714 and Copilot May 25, 2026 06:50

Copilot started reviewing on behalf of Avenger-285714 May 25, 2026 06:50 View session

sourcery-ai Bot reviewed May 25, 2026

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deepin-ci-robot added the approved label May 25, 2026

dongert approved these changes May 25, 2026

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Copilot AI reviewed May 25, 2026

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genksyms: Support arm64 CRC32 hardware acceleration

94b44fd

maillist inclusion category: performance Use hardware 'crc32b' to build genksyms when support, it shows 2x speed up than crctab32 way. Signed-off-by: Wentao Guan <guanwentao@uniontech.com>

opsiff force-pushed the linux-6.18.y-2026-05-25 branch from 16b048d to 94b44fd Compare May 25, 2026 06:59

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Summary by Sourcery

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Reviewer's Guide

Sequence diagram for arm64 CRC32 hardware acceleration in genksyms

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Pull request overview

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opsiff commented May 25, 2026

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