Re: [RFC v1 12/19] ptwrite uprobes: Add pacing to the probes

[sashiko-bot@kernel.org]

> When PTWRITEs are too tightly spaced they can lose data. While the decoder
> makes some effort to recover from this it can be still annoying for the
> user. This patch adds LFENCEs between the individual instructions to
> mimimize (mostly avoid) this problem. It can still happen with parallel
> branch collection or if a high frequency of timing packets are configured.
> The extend also depends on the core-type.
> 
> It can be still disabled with %nopace. This is useful when the user knows
> the probes are not too tightly spaced. It is usually still needed
> with many arguments.
> 
> This patch generates LFENCEs for the probes unless disabled.
> 
> Compared with %nopace, default pacing increases probe cost by roughly 272%
> with PT off, 227% with full tracing, and 48% in snapshot mode on Alder Lake.
> 
> Assisted-by: omp:gpt-5.6-luna
> Signed-off-by: Andi Kleen <ak@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260831150651.1134594-1-ak@kernel.org?part=12