linux-kernel - [RFC][Patch 03/18] sched: use u64 for load

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Message-Id: <1303332697-16426-4-git-send-email-ncrao@google.com>
Date:	Wed, 20 Apr 2011 13:51:22 -0700
From:	Nikhil Rao <ncrao@...gle.com>
To:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>
Cc:	Paul Turner <pjt@...gle.com>, Mike Galbraith <efault@....de>,
	linux-kernel@...r.kernel.org, Nikhil Rao <ncrao@...gle.com>
Subject: [RFC][Patch 03/18] sched: use u64 for load_weight fields

This patch converts load_weight fields to use u64 instead of unsigned long.
This is effectively a no-op for 64-bit where unsigned long is 64-bit wide
anyway. On 32-bit architectures, it is required to ensure the rq load weight
does not overflow in the presence of multiple large weight entities. Also
increase MAX_SHARES to 2^28 (from 2^18).

Signed-off-by: Nikhil Rao <ncrao@...gle.com>
---
 include/linux/sched.h |    2 +-
 kernel/sched_debug.c  |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index d2c3bab..6d88be1 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1104,7 +1104,7 @@ struct sched_class {
 };
 
 struct load_weight {
-	unsigned long weight, inv_weight;
+	u64 weight, inv_weight;
 };
 
 #ifdef CONFIG_SCHEDSTATS
diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c
index 7bacd83..d22b666 100644
--- a/kernel/sched_debug.c
+++ b/kernel/sched_debug.c
@@ -201,7 +201,7 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
 	SEQ_printf(m, "  .%-30s: %d\n", "nr_spread_over",
 			cfs_rq->nr_spread_over);
 	SEQ_printf(m, "  .%-30s: %ld\n", "nr_running", cfs_rq->nr_running);
-	SEQ_printf(m, "  .%-30s: %ld\n", "load", cfs_rq->load.weight);
+	SEQ_printf(m, "  .%-30s: %lld\n", "load", cfs_rq->load.weight);
 #ifdef CONFIG_FAIR_GROUP_SCHED
 #ifdef CONFIG_SMP
 	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "load_avg",
@@ -264,7 +264,7 @@ static void print_cpu(struct seq_file *m, int cpu)
 	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", #x, SPLIT_NS(rq->x))
 
 	P(nr_running);
-	SEQ_printf(m, "  .%-30s: %lu\n", "load",
+	SEQ_printf(m, "  .%-30s: %llu\n", "load",
 		   rq->load.weight);
 	P(nr_switches);
 	P(nr_load_updates);
-- 
1.7.3.1

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