From: Dave Chinner <david@fromorbit.com>
To: Alex Elder <aelder@sgi.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCHv2 8/10] xfs: avoid repeated pointer dereferences
Date: Mon, 12 Apr 2010 16:56:44 +1000 [thread overview]
Message-ID: <20100412065644.GJ2493@dastard> (raw)
In-Reply-To: <1270852242.7840.158.camel@doink>
On Fri, Apr 09, 2010 at 05:30:42PM -0500, Alex Elder wrote:
> In xlog_find_cycle_start() use a local variable for some repeated
> operations rather than constantly updating the memory location
> whose address is passed in.
Won't the compiler optimise that out for us? i.e. does the dissassembly
of the function look any better before and after this change?
> Signed-off-by: Alex Elder <aelder@sgi.com>
>
> ---
> fs/xfs/xfs_log_recover.c | 83 ++++++++++++++++++++++++-----------------------
> fs/xfs/xfs_log_recover.c | 26 ++++++++++++++------------
> 1 file changed, 14 insertions(+), 12 deletions(-)
>
> Index: b/fs/xfs/xfs_log_recover.c
> ===================================================================
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -354,26 +354,28 @@ xlog_find_cycle_start(
> {
> xfs_caddr_t offset;
> xfs_daddr_t mid_blk;
> + xfs_daddr_t end_blk;
> uint mid_cycle;
> int error;
>
> - mid_blk = BLK_AVG(first_blk, *last_blk);
> - while (mid_blk != first_blk && mid_blk != *last_blk) {
> + ASSERT(last_blk != NULL);
> + end_blk = *last_blk;
FWIW, there is no need for that ASSERT there - the machine will
panic on the very next line, anyway....
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2010-04-13 1:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-09 22:30 [PATCHv2 8/10] xfs: avoid repeated pointer dereferences Alex Elder
2010-04-12 6:56 ` Dave Chinner [this message]
2010-04-14 21:02 ` Alex Elder
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