linux-kernel - Re: [patch 04/15] sched: validate CFS quota hierarchies

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Date:	Tue, 10 May 2011 16:20:40 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Paul Turner <pjt@...gle.com>
CC:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>, Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [patch 04/15] sched: validate CFS quota hierarchies

Description typos + one bug.

(2011/05/03 18:28), Paul Turner wrote:
> Add constraints validation for CFS bandwidth hierachies.

                                               hierarchies

> 
> Validate that:
>    sum(child bandwidth) <= parent_bandwidth
> 
> In a quota limited hierarchy, an unconstrainted entity

                                   unconstrained

> (e.g. bandwidth==RUNTIME_INF) inherits the bandwidth of its parent.
> 
> Since bandwidth periods may be non-uniform we normalize to the maximum allowed
> period, 1 second.
> 
> This behavior may be disabled (allowing child bandwidth to exceed parent) via
> kernel.sched_cfs_bandwidth_consistent=0
> 
> Signed-off-by: Paul Turner <pjt@...gle.com>
> 
> ---
(snip)
> +/*
> + * normalize group quota/period to be quota/max_period
> + * note: units are usecs
> + */
> +static u64 normalize_cfs_quota(struct task_group *tg,
> +			       struct cfs_schedulable_data *d)
> +{
> +	u64 quota, period;
> +
> +	if (tg == d->tg) {
> +		period = d->period;
> +		quota = d->quota;
> +	} else {
> +		period = tg_get_cfs_period(tg);
> +		quota = tg_get_cfs_quota(tg);
> +	}
> +
> +	if (quota == RUNTIME_INF)
> +		return RUNTIME_INF;
> +
> +	return to_ratio(period, quota);
> +}

Since tg_get_cfs_quota() doesn't return RUNTIME_INF but -1,
this function needs a fix like following.

For fixed version, feel free to add:

Reviewed-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>

Thanks,
H.Seto

---
 kernel/sched.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index d2562aa..f171ba5 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -9465,16 +9465,17 @@ static u64 normalize_cfs_quota(struct task_group *tg,
 	u64 quota, period;
 
 	if (tg == d->tg) {
+		if (d->quota == RUNTIME_INF)
+			return RUNTIME_INF;
 		period = d->period;
 		quota = d->quota;
 	} else {
+		if (tg_cfs_bandwidth(tg)->quota == RUNTIME_INF)
+			return RUNTIME_INF;
 		period = tg_get_cfs_period(tg);
 		quota = tg_get_cfs_quota(tg);
 	}
 
-	if (quota == RUNTIME_INF)
-		return RUNTIME_INF;
-
 	return to_ratio(period, quota);
 }
 

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