[PATCH] RCU: remove alignment padding from rcu_data on 64 bitbuilds
From: Richard Kennedy
Date: Thu May 05 2011 - 11:50:14 EST
Reorder rcu_data to remove 8 bytes of alignment padding on 64 bit builds
so saving a total of 16 bytes per cpu, (rcu_sched_data & rcu_bh_data).
When CONFIG_NO_HZ is set, it shrinks the size of this structure from 264
to 256 bytes allowing it to fit into one fewer cache lines.
Signed-off-by: Richard Kennedy <richard@xxxxxxxxxxxxxxx>
---
patch against v2.6.39-rc6
compiled & tested on x86_64
I've been running with this patch for some weeks and have not seen any
issues.
regards
Richard
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index e8f057e..fcced0f 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -176,6 +176,9 @@ struct rcu_data {
bool qs_pending; /* Core waits for quiesc state. */
bool beenonline; /* CPU online at least once. */
bool preemptable; /* Preemptable RCU? */
+
+ int cpu;
+
struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
unsigned long grpmask; /* Mask to apply to leaf qsmask. */
@@ -238,8 +241,6 @@ struct rcu_data {
unsigned long n_rp_gp_started;
unsigned long n_rp_need_fqs;
unsigned long n_rp_need_nothing;
-
- int cpu;
};
/* Values for signaled field in struct rcu_state. */
--
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