Date: Tue, 2 Dec 2014 22:03:01 +0100
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Subject: Re: [PATCH 5/5] kvm: optimize GFN to memslot lookup with large slots
 amount
Message-ID: <20141202210300.GA13037@potion.redhat.com>
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 <20141202173350.GA11312@potion.brq.redhat.com>
 <547E08C1.3090708@redhat.com>
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2014-12-02 19:45+0100, Paolo Bonzini:
> On 02/12/2014 18:33, Radim Krčmář wrote:
> >> > +	while (start < end) {
> >> > +		slot = start + (end - start) / 2;
> >> > +
> >> > +		if (gfn >= memslots[slot].base_gfn)
> > (Even thought division is costly, I think that checking here if 'slot'
> >  is the one we want wouldn't help very much.)
> > 
> 
> Division by an unsigned is just a right shift.  Division by signed
> integer is a right shift + conditional move.  We can change / 2 to
> explicit >> 1, or change start and end to unsigned, or both.

My bad, no respectable optimizer would miss that.
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