From: Kees Cook <keescook@chromium.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>, Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: [PATCH] sched: task_struct: Fill unconditional hole induced by sched_entity
Date: Thu, 23 Sep 2021 19:54:50 -0700 [thread overview]
Message-ID: <20210924025450.4138503-1-keescook@chromium.org> (raw)
With struct sched_entity before the other sched entities, its alignment
won't induce a struct hole. This saves 64 bytes in defconfig task_struct:
Before:
...
unsigned int rt_priority; /* 120 4 */
/* XXX 4 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
const struct sched_class * sched_class; /* 128 8 */
/* XXX 56 bytes hole, try to pack */
/* --- cacheline 3 boundary (192 bytes) --- */
struct sched_entity se __attribute__((__aligned__(64))); /* 192 448 */
/* --- cacheline 10 boundary (640 bytes) --- */
struct sched_rt_entity rt; /* 640 48 */
struct sched_dl_entity dl __attribute__((__aligned__(8))); /* 688 224 */
/* --- cacheline 14 boundary (896 bytes) was 16 bytes ago --- */
After:
...
unsigned int rt_priority; /* 120 4 */
/* XXX 4 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
struct sched_entity se __attribute__((__aligned__(64))); /* 128 448 */
/* --- cacheline 9 boundary (576 bytes) --- */
struct sched_rt_entity rt; /* 576 48 */
struct sched_dl_entity dl __attribute__((__aligned__(8))); /* 624 224 */
/* --- cacheline 13 boundary (832 bytes) was 16 bytes ago --- */
Summary diff:
- /* size: 7040, cachelines: 110, members: 188 */
+ /* size: 6976, cachelines: 109, members: 188 */
Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/linux/sched.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 39039ce8ac4c..27ed1d40028f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -775,10 +775,10 @@ struct task_struct {
int normal_prio;
unsigned int rt_priority;
- const struct sched_class *sched_class;
struct sched_entity se;
struct sched_rt_entity rt;
struct sched_dl_entity dl;
+ const struct sched_class *sched_class;
#ifdef CONFIG_SCHED_CORE
struct rb_node core_node;
--
2.30.2
next reply other threads:[~2021-09-24 2:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-24 2:54 Kees Cook [this message]
2021-10-06 4:48 ` [PATCH] sched: task_struct: Fill unconditional hole induced by sched_entity Kees Cook
2021-10-06 9:27 ` Peter Zijlstra
2021-10-06 16:31 ` Kees Cook
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