Message-ID: <546611E5.2090209@redhat.com>
Date: Fri, 14 Nov 2014 15:29:57 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>
CC: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        yoshikawa_takuya_b1@lab.ntt.co.jp, imammedo@redhat.com
Subject: Re: [PATCH 1/3] kvm: memslots: track id_to_index changes during the
 insertion sort
References: <1415963522-5255-1-git-send-email-pbonzini@redhat.com> <1415963522-5255-2-git-send-email-pbonzini@redhat.com> <20141114133500.GA10593@potion.brq.redhat.com>
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On 14/11/2014 14:35, Radim Krčmář wrote:
> We are replacing in a sorted array, so the the direction of our
> traversal doesn't change, (and we could lose one tab level here,)
> 
> 	if (new->npages < mslots[i].npages) {
> 		while (i < (KVM_MEM_SLOTS_NUM - 1) &&
> 		       new->npages < mslots[i + 1].npages) {
> 			mslots[i] = mslots[i + 1];
> 			slots->id_to_index[mslots[i].id] = i;
> 			i++;
> 		}
> 	else if (new->npages > mslots[i].npages)
> 		while (i > 0 &&
> 		       new->npages > mslots[i - 1].npages) {
> 			mslots[i] = mslots[i - 1];
> 			slots->id_to_index[mslots[i].id] = i;
> 			i--;
> 		}
> 
> (I guess you don't want me to abstract these two loops further :)

Right.  You do not need the "else if" as long as you keep the outer "if
(new->npages != mslots[i].npages)".

> (We'll have to change it into an interval tree, or something, if the
>  number of slots rises anyway.)

I don't think that's needed, actually.  gfn_to_page and gfn_to_memslot
are very rarely in the profiles with EPT.

Paolo
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