linux-kernel - Re: [RFC] Alignment of fields in struct dentry

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Date:	Fri, 15 Sep 2006 22:44:07 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Jörn Engel <joern@...nheim.fh-wedel.de>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] Alignment of fields in struct dentry

Am Friday 15 September 2006 12:27 schrieb Jörn Engel:
> -};
> +}__attribute__((aligned(64))); /* make sure the dentry is 128/192 bytes
> +                                  on 32/64 bit independently of config
> +                                  options.  d_iname will vary in length
> +                                  a bit. */

I'd guess that a 32 byte alignment is much better here, 64 byte sounds
excessive. It should have the same effect with the current dentry layout
and default config options, but would keep the d_iname length in the
16-44 byte range instead of 16-76 byte as your patch does.

Since all important fields are supposed to be kept in 32 bytes anyway,
they are still either at the start or the end of a given cache line,
but never cross two.

	Arnd <><
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