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authorEric Dumazet <dada1@cosmosbay.com>2006-12-06 20:38:44 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-07 08:39:40 -0800
commit1c69d921ed9cc6593ad4f60c0f9951cb0d62b0b4 (patch)
tree669149c112fd917d68a301b2bcceae681af17a1c
parent9a0efbb8795e8c5acb279d984b53d6af6ecdd00f (diff)
downloadop-kernel-dev-1c69d921ed9cc6593ad4f60c0f9951cb0d62b0b4.zip
op-kernel-dev-1c69d921ed9cc6593ad4f60c0f9951cb0d62b0b4.tar.gz
[PATCH] rcu: add a prefetch() in rcu_do_batch()
On some workloads, (for example when lot of close() syscalls are done), RCU qlen can be quite large, and RCU heads are no longer in cpu cache when rcu_do_batch() is called. This patch adds a prefetch() in rcu_do_batch() to give CPU a hint to bring back cache lines containing 'struct rcu_head's. Most list manipulations macros include prefetch(), but not open coded ones (at least with current C compilers :) ) I got a nice speedup on a trivial benchmark (3.48 us per iteration instead of 3.95 us on a 1.6 GHz Pentium-M) while (1) { pipe(p); close(fd[0]); close(fd[1]);} Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--kernel/rcupdate.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 26bb5ff..3554b76 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -235,12 +235,14 @@ static void rcu_do_batch(struct rcu_data *rdp)
list = rdp->donelist;
while (list) {
- next = rdp->donelist = list->next;
+ next = list->next;
+ prefetch(next);
list->func(list);
list = next;
if (++count >= rdp->blimit)
break;
}
+ rdp->donelist = list;
local_irq_disable();
rdp->qlen -= count;
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