From: Theodore Ts'o <tytso@mit.edu>
To: Lukas Czerner <lczerner@redhat.com>
Cc: linux-ext4@vger.kernel.org
Subject: Re: [PATCH 2/2] ext4: introduce ext4_get_group_number()
Date: Tue, 26 Mar 2013 23:12:07 -0400 [thread overview]
Message-ID: <20130327031207.GC5861@thunk.org> (raw)
In-Reply-To: <1364207051-27037-2-git-send-email-lczerner@redhat.com>
On Mon, Mar 25, 2013 at 11:24:11AM +0100, Lukas Czerner wrote:
> Currently on many places in ext4 we're using
> ext4_get_group_no_and_offset() even though we're only interested in
> knowing the block group of the particular block, not the offset within
> the block group so we can use more efficient way to compute block group.
>
> This patch introduces ext4_get_group_number() which computes block group
> for a givem block much more efficiently. Use this function instead of
> ext4_get_group_no_and_offset() everywhere where we're only interested in
> knowing the block group.
Again, we have the same problem as the previous patch. I could
imagine setting a flag which uses the shift-instead-of-div
optimization, but that will reduce the optimization somewhat. OTOH,
an 64-bit division is pretty expensive, especially on older/simpler
CPU's, so perhaps it's worth it.
- Ted
next prev parent reply other threads:[~2013-03-27 3:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-25 10:24 [PATCH 1/2] ext4: Make ext4_block_in_group() much more efficient Lukas Czerner
2013-03-25 10:24 ` [PATCH 2/2] ext4: introduce ext4_get_group_number() Lukas Czerner
2013-03-27 3:12 ` Theodore Ts'o [this message]
2013-03-27 3:44 ` Theodore Ts'o
2013-03-27 3:05 ` [PATCH 1/2] ext4: Make ext4_block_in_group() much more efficient Theodore Ts'o
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