From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Xiaoliang \(David\) Wei" <weixl@caltech.edu>
Subject: Re: packet re-ordering on SMP machines.
Date: Tue, 27 Aug 2002 12:43:02 -0700
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Cc: "Ben Greear" <greearb@candelatech.com>,
   "Cheng Jin" <chengjin@cs.caltech.edu>, "Cheng Hu" <chenghu@cs.caltech.edu>,
   "Steven Low" <slow@cs.caltech.edu>, <netdev@oss.sgi.com>
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To: "jamal" <hadi@cyberus.ca>, "Andi Kleen" <ak@suse.de>
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> >
> > That is because of the lock it takes. Locks are always slow.
>
> xtime_lock?
I guess so, after looked at do_gettimeofday

>
> > Possibilities:
> >
> > - Ignore the problem and switch back to gettimeoffset again
>
> Is it safe to call gettimeoffset without the lock?
What's the possible danger to ignore the lock? Can I read the xtime
directly?

>
> > - Switch to gettimeoffset but add some correction step for the unlikely
> > case that someone wants the timestamp from user space
> > (would be my prefered solution)
> > - Implement lockless gettimeofday like x86-64 or sparc
> > (good one too, but likely slower than last)
>
>
> ia64 seems to also have the lock.
>
> cheers,
> jamal
>
>
>
>