From: Theodore Tso <tytso@mit.edu>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: a.p.zijlstra@chello.nl, dada1@cosmosbay.com,
linux-kernel@vger.kernel.org, davem@davemloft.net,
cmm@us.ibm.com, linux-ext4@vger.kernel.org
Subject: Re: [PATCH] percpu_counter: Fix __percpu_counter_sum()
Date: Mon, 8 Dec 2008 18:49:27 -0500 [thread overview]
Message-ID: <20081208234927.GF2501@mit.edu> (raw)
In-Reply-To: <20081208150724.37761534.akpm@linux-foundation.org>
On Mon, Dec 08, 2008 at 03:07:24PM -0800, Andrew Morton wrote:
> > Stupid question --- if you're worried about cacheline ping-pongs, why
> > aren't each cpu's delta counter cacheline aligned?
>
> They are allocated with alloc_percpu(), so each CPU's counter lives
> in a per-cpu area. If you chase through seventeen layers of Rustyness
> you end up at mm/allocpercpu.c:percpu_populate() which is where that
> little s32 ends up getting allocated.
Ah, OK. So the answer is "Ted was stupid and didn't understand n
layers of percpu abstractions".... whoever wrote that code seems to
have been a great believer of the saying, "if the code was hard to
*write*, it should be hard to *understand*". :-)
- Ted
next prev parent reply other threads:[~2008-12-08 23:49 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-03 18:40 [PATCH] percpu_counter: fix CPU unplug race in percpu_counter_destroy() Eric Dumazet
2008-12-03 20:24 ` [PATCH] percpu_counter: Fix __percpu_counter_sum() Eric Dumazet
2008-12-03 20:45 ` Peter Zijlstra
2008-12-04 6:14 ` David Miller
2008-12-07 4:22 ` Andrew Morton
2008-12-07 4:22 ` Andrew Morton
2008-12-07 10:25 ` Peter Zijlstra
2008-12-07 13:28 ` Eric Dumazet
2008-12-07 13:28 ` Eric Dumazet
2008-12-07 17:28 ` Andrew Morton
2008-12-07 18:00 ` Eric Dumazet
2008-12-07 18:00 ` Eric Dumazet
2008-12-08 4:52 ` Andrew Morton
2008-12-08 22:12 ` Theodore Tso
2008-12-08 22:20 ` Peter Zijlstra
2008-12-08 23:00 ` Theodore Tso
2008-12-08 23:05 ` Peter Zijlstra
2008-12-08 23:08 ` Peter Zijlstra
2008-12-09 8:12 ` Eric Dumazet
2008-12-09 8:12 ` Eric Dumazet
2008-12-09 8:34 ` Peter Zijlstra
2008-12-09 8:34 ` Peter Zijlstra
2008-12-10 5:09 ` Eric Dumazet
2008-12-10 5:49 ` Andrew Morton
2008-12-10 22:56 ` Eric Dumazet
2008-12-10 22:56 ` Eric Dumazet
2008-12-12 8:17 ` Rusty Russell
2008-12-12 8:22 ` Eric Dumazet
2008-12-12 8:22 ` Eric Dumazet
2008-12-12 11:08 ` [PATCH] percpu_counter: use local_t and atomic_long_t if possible Eric Dumazet
2008-12-12 11:08 ` Eric Dumazet
2008-12-12 11:29 ` Peter Zijlstra
2008-12-23 11:43 ` Peter Zijlstra
2008-12-25 13:26 ` Rusty Russell
2008-12-15 12:53 ` [PATCH] percpu_counter: Fix __percpu_counter_sum() Rusty Russell
2008-12-16 20:16 ` Ingo Molnar
2008-12-10 7:12 ` Peter Zijlstra
2008-12-08 23:07 ` Andrew Morton
2008-12-08 23:49 ` Theodore Tso [this message]
2008-12-08 22:22 ` Andrew Morton
2008-12-08 22:44 ` Mingming Cao
2008-12-08 22:44 ` Mingming Cao
2008-12-07 22:24 ` [PATCH] atomic: fix a typo in atomic_long_xchg() Eric Dumazet
2008-12-07 22:24 ` Eric Dumazet
2008-12-07 15:28 ` [PATCH] percpu_counter: Fix __percpu_counter_sum() Theodore Tso
2008-12-08 4:42 ` Andrew Morton
2008-12-08 17:55 ` Mingming Cao
2008-12-08 17:55 ` Mingming Cao
2008-12-11 16:32 ` [stable] " Greg KH
2008-12-08 17:44 ` Mingming Cao
2008-12-08 17:44 ` Mingming Cao
2008-12-04 6:13 ` [PATCH] percpu_counter: fix CPU unplug race in percpu_counter_destroy() David Miller
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