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McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org, Dimitri Sivanich , "Paul E. McKenney" Subject: [PATCH tip/core/rcu 08/23] rcu: Segregate rcu_state fields to improve cache locality Date: Thu, 30 Aug 2012 11:18:23 -0700 Message-Id: <1346350718-30937-8-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1346350718-30937-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120830181811.GA29154@linux.vnet.ibm.com> <1346350718-30937-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12083018-7282-0000-0000-00000C74E40B X-Gm-Message-State: ALoCoQlBOV6JjOKYG84bPDcWexC750J8u3zn0Vz9adxk1kGm7eBYeLff0XFrg5qJTbL0snQxl/tb From: Dimitri Sivanich The fields in the rcu_state structure that are protected by the root rcu_node structure's ->lock can share a cache line with the fields protected by ->onofflock. This can result in excessive memory contention on large systems, so this commit applies ____cacheline_internodealigned_in_smp to the ->onofflock field in order to segregate them. Signed-off-by: Dimitri Sivanich Signed-off-by: Paul E. McKenney Tested-by: Dimitri Sivanich Reviewed-by: Josh Triplett --- kernel/rcutree.h | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/kernel/rcutree.h b/kernel/rcutree.h index effb273..5d92b80 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -394,7 +394,8 @@ struct rcu_state { /* End of fields guarded by root rcu_node's lock. */ - raw_spinlock_t onofflock; /* exclude on/offline and */ + raw_spinlock_t onofflock ____cacheline_internodealigned_in_smp; + /* exclude on/offline and */ /* starting new GP. */ struct rcu_head *orphan_nxtlist; /* Orphaned callbacks that */ /* need a grace period. */