Re: [RFT/PATCH v2 2/6] x86-64: Optimize vread_tsc's barriers
From: Andi Kleen
Date: Thu Apr 07 2011 - 12:42:52 EST
> But before that, I would check that the second lfence is needed AT
> ALL. I don't know whether we ever tried the "only barrier before"
> version, because quite frankly, if you call this thing in a loop, then
> a single barrier will still mean that there are barriers in between
> iterations. So...
The testers will call it in a loop, but real users (e.g. using it for
a logging timestamp) may not.
I'm sure a single barrier would have fixed the testers, as you point out,
but the goal wasn't to only fix testers.
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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