From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org, l_indien@magic.fr
Cc: Alexander Graf <agraf@suse.de>
Subject: Re: [Fwd: Re: [Qemu-devel] [PATCH] SVM support]
Date: Wed, 19 Sep 2007 16:35:49 +0100 [thread overview]
Message-ID: <200709191635.51270.paul@codesourcery.com> (raw)
In-Reply-To: <1190212770.12194.16.camel@jma4.dev.netgem.com>
> > >> OK, great. Having 64 bits may also help for additional (ie future...)
> > >> features in PowerPC 64 emulation.
> > >
> > > Maybe worth letting the target say whether it needs 32 or 64-bit
> > > flags.
> > > The flag lookup is likely to be on a hot path.
> > >
>
> I may be wrong, but it seems to me that TB flags are only used to be
> compared in tb_find_fast and tb_find_slow, which are not a very fast
> path (we come here when we cannot jump directly to the next tb and are
> not in the most time critical code) then we can afford adding a few asm
> instructions (I would say max 2 ?) to replace a 32 bits comparison with
> a 64 bits one. My feeling is that the performance loss here won't be
> sensible, but that may need to be proved.
For some reason I thought the flags were also used in the hash lookup. This is
not the case, so I withdraw my objection.
Paul
next prev parent reply other threads:[~2007-09-19 15:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-18 20:54 [Fwd: Re: [Qemu-devel] [PATCH] SVM support] J. Mayer
2007-09-18 23:05 ` J. Mayer
2007-09-18 23:28 ` Paul Brook
2007-09-19 10:55 ` Alexander Graf
2007-09-19 10:56 ` Alexander Graf
2007-09-19 14:39 ` Jocelyn Mayer
2007-09-19 14:55 ` Alexander Graf
2007-09-19 15:35 ` Paul Brook [this message]
2007-09-19 18:24 ` J. Mayer
2007-09-19 10:59 ` Alexander Graf
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