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Commit 8a143426 authored by Eric Dumazet's avatar Eric Dumazet Committed by Linus Torvalds
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[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: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 2ecb9e63

fs/buffer.c

+4 −1
Original line number Diff line number Diff line
@@ -3078,7 +3078,7 @@ static void recalc_bh_state(void) 
	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 @@ static void buffer_exit_cpu(int cpu) 
		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,