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Date: Mon, 8 Dec 2008 18:49:27 -0500 From: Theodore Tso <tytso@....edu> To: Andrew Morton <akpm@...ux-foundation.org> Cc: a.p.zijlstra@...llo.nl, dada1@...mosbay.com, linux-kernel@...r.kernel.org, davem@...emloft.net, cmm@...ibm.com, linux-ext4@...r.kernel.org Subject: Re: [PATCH] percpu_counter: Fix __percpu_counter_sum() 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 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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