From: Paolo Bonzini <pbonzini@redhat.com>
To: "Radim Krčmář" <rkrcmar@redhat.com>,
"Igor Mammedov" <imammedo@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH 5/5] kvm: optimize GFN to memslot lookup with large slots amount
Date: Tue, 02 Dec 2014 19:45:21 +0100 [thread overview]
Message-ID: <547E08C1.3090708@redhat.com> (raw)
In-Reply-To: <20141202173350.GA11312@potion.brq.redhat.com>
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.
Paolo
next prev parent reply other threads:[~2014-12-02 18:45 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-01 17:29 [PATCH 0/5] kvm: memslots lookup optimization Igor Mammedov
2014-12-01 17:29 ` [PATCH 1/5] kvm: update_memslots: drop not needed check for the same number of pages Igor Mammedov
2014-12-01 17:29 ` [PATCH 2/5] kvm: update_memslots: drop not needed check for the same slot Igor Mammedov
2014-12-01 17:29 ` [PATCH 3/5] kvm: search_memslots: add simple LRU memslot caching Igor Mammedov
2014-12-01 17:29 ` [PATCH 4/5] kvm: change memslot sorting rule from size to GFN Igor Mammedov
2014-12-01 17:29 ` [PATCH 5/5] kvm: optimize GFN to memslot lookup with large slots amount Igor Mammedov
2014-12-02 17:33 ` Radim Krčmář
2014-12-02 18:45 ` Paolo Bonzini [this message]
2014-12-02 21:03 ` Radim Krčmář
2014-12-01 17:38 ` [PATCH 0/5] kvm: memslots lookup optimization Paolo Bonzini
2014-12-02 7:57 ` Igor Mammedov
2014-12-02 13:24 ` Paolo Bonzini
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