[PATCH] HOTPLUG_CPU: avoid hitting too many cachelines in recalc_bh_state()
Instead of using for_each_cpu(i), we can use for_each_online_cpu(i).
When a CPU goes offline (ie removed from online map), it might have a non
null bh_accounting.nr, so this patch adds a transfer of this counter to an
online CPU counter.
We already have a hotcpu_notifier, (function buffer_cpu_notify()), where we
can do this bh_accounting.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/buffer.c b/fs/buffer.c
index 36c7253..11ca6eb 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3078,7 +3078,7 @@
if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
return;
__get_cpu_var(bh_accounting).ratelimit = 0;
- for_each_cpu(i)
+ for_each_online_cpu(i)
tot += per_cpu(bh_accounting, i).nr;
buffer_heads_over_limit = (tot > max_buffer_heads);
}
@@ -3127,6 +3127,9 @@
brelse(b->bhs[i]);
b->bhs[i] = NULL;
}
+ get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
+ per_cpu(bh_accounting, cpu).nr = 0;
+ put_cpu_var(bh_accounting);
}
static int buffer_cpu_notify(struct notifier_block *self,