linux-kernel - [PATCH v1 0/4] Kill the time spent in patch

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Message-Id: <cover.1647962456.git.christophe.leroy@csgroup.eu>
Date:   Tue, 22 Mar 2022 16:40:17 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v1 0/4] Kill the time spent in patch_instruction()

This series reduces by 70% the time required to activate
ftrace on an 8xx with CONFIG_STRICT_KERNEL_RWX.

Measure is performed in function ftrace_replace_code() using mftb()
around the loop.

With the series,
- Without CONFIG_STRICT_KERNEL_RWX, 416000 TB ticks are measured.
- With CONFIG_STRICT_KERNEL_RWX, 546000 TB ticks are measured.

Before this series,
- Without CONFIG_STRICT_KERNEL_RWX, 427000 TB ticks are measured.
- With CONFIG_STRICT_KERNEL_RWX, 1744000 TB ticks are measured.

Before the series, CONFIG_STRICT_KERNEL_RWX multiplies the time
required for ftrace activation by more than 4.

With the series, CONFIG_STRICT_KERNEL_RWX increases the time
required for ftrace activation by only 30%

Christophe Leroy (4):
  powerpc/code-patching: Don't call is_vmalloc_or_module_addr() without
    CONFIG_MODULES
  powerpc/code-patching: Speed up page mapping/unmapping
  powerpc/code-patching: Use jump_label for testing freed initmem
  powerpc/code-patching: Use jump_label to check if poking_init() is
    done

 arch/powerpc/include/asm/code-patching.h |  2 ++
 arch/powerpc/lib/code-patching.c         | 37 +++++++++++++++---------
 arch/powerpc/mm/mem.c                    |  2 ++
 3 files changed, 28 insertions(+), 13 deletions(-)

-- 
2.35.1