Messages in this thread |  | | | From | Andi Kleen <> | | Subject | Re: [PATCH] use unlikely() for current_kernel_time() loop | | Date | Thu, 8 Jun 2006 07:39:33 +0200 |
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On Thursday 08 June 2006 07:01, Andrew Morton wrote: > On 08 Jun 2006 04:28:12 +0200 > Andi Kleen <ak@suse.de> wrote: > > > Andreas Dilger <adilger@clusterfs.com> writes: > > > > > Hello, > > > I just noticed this minor optimization. current_kernel_time() is called > > > from current_fs_time() so it is used fairly often but it doesn't use > > > unlikely(read_seqretry(&xtime_lock, seq)) as other users of xtime_lock do. > > > Also removes extra whitespace on the empty line above. > > > > It would be better to put the unlikely into the read_seqretry I guess. > > > > yup. But it'd be good to check that this actually causes the compiler to > do the right thing, rather than simply ignoring it.
If it was put into a macro wrapper it should be safe enough.
> > I'm not sure how one would do that though. I guess compare > before-and-after assembly code, work out if "after" is better.
Nothing on x86-64 at least - it uses -fno-reorder-blocks by default.
-Andi
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