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Re: [PATCH] alternative hirate for builtin_expert
- From: Jan Hubicka <hubicka at ucw dot cz>
- To: Rong Xu <xur at google dot com>
- Cc: Jan Hubicka <hubicka at ucw dot cz>, GCC Patches <gcc-patches at gcc dot gnu dot org>, David Li <davidxl at google dot com>
- Date: Wed, 2 Oct 2013 23:31:02 +0200
- Subject: Re: [PATCH] alternative hirate for builtin_expert
- Authentication-results: sourceware.org; auth=none
- References: <CAF1bQ=TH5+Qfd1MsAUDBJj+F-zizymTTGh7HxyuXUbaPqd-mng at mail dot gmail dot com> <CAF1bQ=Q_eiCz8AYkU-c=Xu7quQ0vy8eP=pi9QZt+QOF4vicnsg at mail dot gmail dot com> <20131002160827 dot GB7181 at kam dot mff dot cuni dot cz> <CAF1bQ=Snvzzmm=AEr-crrKhopRugKbcExH+wFCyCcgZZHz+Uow at mail dot gmail dot com>
> Thanks for the suggestion. This is much cleaner than to use binary parameter.
> Just want to make sure I understand it correctly about the orginal hitrate:
> you want to retire the hitrate in PRED_BUILTIN_EXPECT and always use
> the one specified in the biniltin-expect-probability parameter.
> Should I use 90% as the default? It's hard to fit current value 0.9996
> in percent form.
Yes, 90% seems fine. The original value was set quite arbitrarily and no real
performance study was made as far as I know except yours. I think users that
are sure they use expect to gueard completely cold edges may just use 100%
instead of 0.9996, so I would not worry much about the precision.
> > OK with that change.
> > Honza