linux-ext4 - Re: [PATCH] percpu_counter: Fix __percpu_counter

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20081208234927.GF2501@mit.edu>
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