linux-kernel - [PATCH 2/3] sched/cputime: Make nr

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Message-Id: <1472722064-7151-3-git-send-email-sgruszka@redhat.com>
Date:   Thu,  1 Sep 2016 11:27:43 +0200
From:   Stanislaw Gruszka <sgruszka@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Giovanni Gherdovich <ggherdovich@...e.cz>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mike Galbraith <mgalbraith@...e.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Ingo Molnar <mingo@...nel.org>,
        Stanislaw Gruszka <sgruszka@...hat.com>
Subject: [PATCH 2/3] sched/cputime: Make nr_migrations u32 on 32 bit cpus

My previous patch:

("sched/cputime: Improve scalability of times()/clock_gettime() on 32 bit cpus")

add new sum_exec_runtime_seqclock fields to sched_entity struct.

This changed the alignment of other fields of the sched_entity struct.
To preserve previous alignment, which makes variables commonly used
together are kept in a cache line, make nr_migrations field u32 on
32 bit architectures.

This field is used only for debugging and basically nr_migrations
should not be enormous number.

Signed-off-by: Stanislaw Gruszka <sgruszka@...hat.com>
---
 include/linux/sched.h | 5 +++--
 kernel/sched/debug.c  | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 65714bc..b9d9333 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1332,9 +1332,10 @@ struct sched_entity {
 	u64			vruntime;
 	u64			prev_sum_exec_runtime;
 
+#ifdef CONFIG_64BIT
 	u64			nr_migrations;
-
-#ifndef CONFIG_64BIT
+#else
+	u32			nr_migrations;
 	seqcount_t		sum_exec_runtime_seqcount;
 #endif
 
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 2a0a999..db85816 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -921,8 +921,8 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
 
 		avg_per_cpu = p->se.sum_exec_runtime;
 		if (p->se.nr_migrations) {
-			avg_per_cpu = div64_u64(avg_per_cpu,
-						p->se.nr_migrations);
+			avg_per_cpu = div64_ul(avg_per_cpu,
+					       p->se.nr_migrations);
 		} else {
 			avg_per_cpu = -1LL;
 		}
-- 
1.8.3.1