Re: [PATCH 02/16] perf: Add ability to attach registers dump tosample

[Peter Zijlstra]

On Wed, 2012-05-23 at 21:32 +0200, Jiri Olsa wrote:
>  /*
> + * Values for sample_regs when PERF_SAMPLE_REGS is set.
> + * Defines register set to be attached to the sample.
> + */
> +enum perf_sample_regs {
> +       PERF_SAMPLE_REGS_USER   = 1U << 0, /* user registers */
> +       PERF_SAMPLE_REGS_MAX    = 1U << 1, /* non-ABI */
> +};



> +       __u64   sample_regs; /* enum perf_sample_regs */
> +
> +       /*
> +        * Arch specific mask for PERF_SAMPLE_REGS_USER setup.
> +        * Defines set of user regs to dump on samples.
> +        * See asm/perf_regs.h for details.
> +        */
> +       __u64   sample_regs_user; 

This all just smells.. :/

So you're wasting 64 bits to specify PERF_SAMPLE_REGS_USER while also
implying we'll need another u64 for every other value of
perf_sample_regs?

What are we doing here and why?

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