From: Avi Kivity <avi@redhat.com>
To: Zach Brown <zach.brown@oracle.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: packing structures and numbers
Date: Sat, 04 Oct 2008 11:31:19 +0300 [thread overview]
Message-ID: <48E729D7.4030509@redhat.com> (raw)
In-Reply-To: <48E66659.1030202@oracle.com>
Zach Brown wrote:
> Avi Kivity wrote:
>
>> I've been reading btrfs's on-disk format, and two things caught my eye
>>
>> - attribute((packed)) structures everywhere, often with misaligned
>> fields. This conserves space, but can be harmful to in-memory
>> performance on some archs.
>>
>
> How harmful? Do you have any profiles that can even pick this out of
> the noise?
>
On those archs that take faults on unaligned accesses it's unlikely to
be in the noise. But we could (and should) stick a get_unaligned() in
the accessor functions.
uleb128 encoding is orthogonal to this issue, however. It's only about
getting better density.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2008-10-04 8:31 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-03 11:42 packing structures and numbers Avi Kivity
2008-10-03 12:22 ` Chris Mason
2008-10-03 13:40 ` Avi Kivity
2008-10-04 0:22 ` Daniel Phillips
2008-10-04 0:28 ` Chris Mason
2008-10-04 0:35 ` Daniel Phillips
2008-10-04 0:43 ` Daniel Phillips
2008-10-04 8:27 ` Avi Kivity
2008-10-03 18:37 ` Zach Brown
2008-10-04 8:31 ` Avi Kivity [this message]
2008-10-04 16:34 ` Andi Kleen
2008-10-05 5:31 ` Avi Kivity
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