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Message-ID: <20190830094505.GA2369@hirez.programming.kicks-ass.net>
Date: Fri, 30 Aug 2019 11:45:05 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Patrick Bellasi <patrick.bellasi@....com>
Cc: linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
linux-api@...r.kernel.org, cgroups@...r.kernel.org,
Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Viresh Kumar <viresh.kumar@...aro.org>,
Paul Turner <pjt@...gle.com>, Michal Koutny <mkoutny@...e.com>,
Quentin Perret <quentin.perret@....com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Morten Rasmussen <morten.rasmussen@....com>,
Juri Lelli <juri.lelli@...hat.com>,
Todd Kjos <tkjos@...gle.com>,
Joel Fernandes <joelaf@...gle.com>,
Steve Muckle <smuckle@...gle.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Alessio Balsini <balsini@...roid.com>
Subject: Re: [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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