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SubjectRe: [PATCH v14 1/6] sched/core: uclamp: Extend CPU's cgroup controller
On Thu, Aug 22, 2019 at 02:28:06PM +0100, Patrick Bellasi wrote:
> +#define _POW10(exp) ((unsigned int)1e##exp)
> +#define POW10(exp) _POW10(exp)

What is this magic? You're forcing a float literal into an integer.
Surely that deserves a comment!

> +struct uclamp_request {
> +#define UCLAMP_PERCENT_SHIFT 2
> +#define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT))
> + s64 percent;
> + u64 util;
> + int ret;
> +};
> +
> +static inline struct uclamp_request
> +capacity_from_percent(char *buf)
> +{
> + struct uclamp_request req = {
> + .percent = UCLAMP_PERCENT_SCALE,
> + .util = SCHED_CAPACITY_SCALE,
> + .ret = 0,
> + };
> +
> + buf = strim(buf);
> + if (strncmp("max", buf, 4)) {

That is either a bug, and you meant to write: strncmp(buf, "max", 3), or
it is not, and then you could've written: strcmp(buf, "max")

But as written it doesn't make sense.

> + req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT,
> + &req.percent);
> + if (req.ret)
> + return req;
> + if (req.percent > UCLAMP_PERCENT_SCALE) {
> + req.ret = -ERANGE;
> + return req;
> + }
> +
> + req.util = req.percent << SCHED_CAPACITY_SHIFT;
> + req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE);
> + }
> +
> + return req;
> +}

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