From: Timothy Shimmin <tes@sgi.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: David Chinner <dgc@sgi.com>, Lachlan McIlroy <lachlan@sgi.com>,
xfs-dev <xfs-dev@sgi.com>, xfs-oss <xfs@oss.sgi.com>
Subject: Re: [Patch] Cacheline align xlog_t
Date: Fri, 04 Apr 2008 12:02:06 +1100 [thread overview]
Message-ID: <47F57E0E.7010700@sgi.com> (raw)
In-Reply-To: <20080403064608.GS29105@one.firstfloor.org>
Andi Kleen wrote:
> On Thu, Apr 03, 2008 at 08:23:47AM +1000, David Chinner wrote:
>>> For the dynamic allocation you would rather need to make sure it
>>> starts at a cache line boundary explicitely because the allocator doesn't
>>> know the alignment of the target type, otherwise your careful
>>> padding might be useless.
>
>> There isn't one, right?
>
> You can always align yourself with kmalloc (or any other arbitary
> size allocator) with the standard technique:
> get L1_CACHE_BYTES-1 or possibly better cache_line_size() - 1 bytes
> more and then align the pointer manually with ALIGN. Only tricky part
> is that you have to undo the alignment before freeing.
>
Yeah, how do you know how much was offset for the alignment
to go back for the freeing. I guess you could also keep the original pointer
or the offset handy (a pain). Or can the allocator help out?
--Tim
next prev parent reply other threads:[~2008-04-04 1:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-01 23:15 [Patch] Cacheline align xlog_t David Chinner
2008-04-02 6:35 ` Lachlan McIlroy
2008-04-02 5:44 ` David Chinner
2008-04-02 8:28 ` Andi Kleen
2008-04-02 22:23 ` David Chinner
2008-04-03 6:46 ` Andi Kleen
2008-04-04 1:02 ` Timothy Shimmin [this message]
2008-04-04 1:18 ` David Chinner
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