From: Catalin Marinas <catalin.marinas@arm.com>
To: will@kernel.org, ast@kernel.org, puranjay@kernel.org,
andrii@kernel.org, mark.rutland@arm.com,
Liao Chang <liaochang1@huawei.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [PATCH v2] arm64: insn: Simulate nop instruction for better uprobe performance
Date: Tue, 15 Oct 2024 19:58:53 +0100 [thread overview]
Message-ID: <172901867521.2735310.14333146229393737694.b4-ty@arm.com> (raw)
In-Reply-To: <20240909071114.1150053-1-liaochang1@huawei.com>
On Mon, 09 Sep 2024 07:11:14 +0000, Liao Chang wrote:
> v2->v1:
> 1. Remove the simuation of STP and the related bits.
> 2. Use arm64_skip_faulting_instruction for single-stepping or FEAT_BTI
> scenario.
>
> As Andrii pointed out, the uprobe/uretprobe selftest bench run into a
> counterintuitive result that nop and push variants are much slower than
> ret variant [0]. The root cause lies in the arch_probe_analyse_insn(),
> which excludes 'nop' and 'stp' from the emulatable instructions list.
> This force the kernel returns to userspace and execute them out-of-line,
> then trapping back to kernel for running uprobe callback functions. This
> leads to a significant performance overhead compared to 'ret' variant,
> which is already emulated.
>
> [...]
Applied to arm64 (for-next/probes), thanks! I fixed it up according to
Mark's comments.
[1/1] arm64: insn: Simulate nop instruction for better uprobe performance
https://git.kernel.org/arm64/c/ac4ad5c09b34
--
Catalin
next prev parent reply other threads:[~2024-10-15 18:58 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-09 7:11 [PATCH v2] arm64: insn: Simulate nop instruction for better uprobe performance Liao Chang
2024-10-09 23:54 ` Andrii Nakryiko
2024-10-10 10:58 ` Mark Rutland
2024-10-10 22:22 ` Andrii Nakryiko
2024-10-10 10:52 ` Mark Rutland
2024-10-21 10:44 ` Liao, Chang
2024-10-15 18:58 ` Catalin Marinas [this message]
2024-10-21 10:45 ` Liao, Chang
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