linux-ext4 - Re: [PATCH 1/2] ext4: Realign trace events structs to make it smaller

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Date:	Sun, 12 Aug 2012 22:29:44 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Anatol Pomozov <anatol.pomozov@...il.com>
Cc:	adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/2] ext4: Realign trace events structs to make it smaller

On Wed, Jul 18, 2012 at 10:07:33AM -0700, Anatol Pomozov wrote:
> Most hardware architectures require that data (including struct fields)
> have to be aligned in memory. To make it happen compiler inserts padding
> between struct fields if they are not aligned correctly.
> 
> Reorder fields to remove paddings and make structures denser. Making data
> smaller saves some memory that is very important for trace events.
> Tracing buffer has limited size and making objects smaller we can put more
> of them without overflowing the tracing buffer.
> 
> To find data struct holes I used 'pahole -H 1 -E -I vmlinux.o' from
> 'dwarves' package.
> 
> Signed-off-by: Anatol Pomozov <anatol.pomozov@...il.com>

Thanks, applied.

						- Ted
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