From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Cornelia Huck <cohuck@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Janosch Frank <frankja@linux.ibm.com>,
kvm@vger.kernel.org, James Hogan <jhogan@kernel.org>,
Joerg Roedel <joro@8bytes.org>,
David Hildenbrand <david@redhat.com>,
linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org,
linux-kernel@vger.kernel.org, Paul Mackerras <paulus@ozlabs.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
linux-arm-kernel@lists.infradead.org,
Marc Zyngier <maz@kernel.org>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
kvmarm@lists.cs.columbia.edu, Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH v2 14/15] KVM: Terminate memslot walks via used_slots
Date: Thu, 24 Oct 2019 13:48:26 -0700 [thread overview]
Message-ID: <20191024204826.GE28043@linux.intel.com> (raw)
In-Reply-To: <5320341c-1abb-610b-8f5e-090a6726a9b1@redhat.com>
On Thu, Oct 24, 2019 at 10:24:09PM +0200, Paolo Bonzini wrote:
> On 24/10/19 21:38, Sean Christopherson wrote:
> > only
> > * its new index into the array is update.
>
> s/update/tracked/?
Ya, tracked is better. Waffled between updated and tracked, chose poorly :-)
> Returns the changed memslot's
> > * current index into the memslots array.
> > */
> > static inline int kvm_memslot_move_backward(struct kvm_memslots *slots,
> > struct kvm_memory_slot *memslot)
> > {
> > struct kvm_memory_slot *mslots = slots->memslots;
> > int i;
> >
> > if (WARN_ON_ONCE(slots->id_to_index[memslot->id] == -1) ||
> > WARN_ON_ONCE(!slots->used_slots))
> > return -1;
> >
> > for (i = slots->id_to_index[memslot->id]; i < slots->used_slots - 1; i++) {
> > if (memslot->base_gfn > mslots[i + 1].base_gfn)
> > break;
> >
> > WARN_ON_ONCE(memslot->base_gfn == mslots[i + 1].base_gfn);
> >
> > /* Shift the next memslot forward one and update its index. */
> > mslots[i] = mslots[i + 1];
> > slots->id_to_index[mslots[i].id] = i;
> > }
> > return i;
> > }
> >
> > /*
> > * Move a changed memslot forwards in the array by shifting existing slots with
> > * a lower GFN toward the back of the array. Note, the changed memslot itself
> > * is not preserved in the array, i.e. not swapped at this time, only its new
> > * index into the array is updated
>
> Same here?
>
> > * Note, slots are sorted from highest->lowest instead of lowest->highest for
> > * historical reasons.
>
> Not just that, the largest slot (with all RAM above 4GB) is also often
> at the highest address at least on x86.
Ah, increasing the odds of a quick hit on lookup...but only when using a
linear search. The binary search starts in the middle, so that
optimization is also historical :-)
> But we could sort them by size now, so I agree to call these historical
> reasons.
That wouldn't work with the binary search though.
> The code itself is fine, thanks for the work on documenting it.
>
> Paolo
>
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next prev parent reply other threads:[~2019-10-24 20:48 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-22 0:35 [PATCH v2 00/15] KVM: Dynamically size memslot arrays Sean Christopherson
2019-10-22 0:35 ` [PATCH v2 01/15] KVM: Reinstall old memslots if arch preparation fails Sean Christopherson
2019-10-23 9:29 ` Christoffer Dall
2019-10-22 0:35 ` [PATCH v2 02/15] KVM: Don't free new memslot if allocation of said memslot fails Sean Christopherson
2019-10-23 9:29 ` Christoffer Dall
2019-10-22 0:35 ` [PATCH v2 03/15] KVM: PPC: Move memslot memory allocation into prepare_memory_region() Sean Christopherson
2019-10-24 11:55 ` kbuild test robot
2019-10-22 0:35 ` [PATCH v2 04/15] KVM: x86: Allocate memslot resources during prepare_memory_region() Sean Christopherson
2019-10-22 0:35 ` [PATCH v2 05/15] KVM: Drop kvm_arch_create_memslot() Sean Christopherson
2019-10-22 0:35 ` [PATCH v2 06/15] KVM: Explicitly free allocated-but-unused dirty bitmap Sean Christopherson
2019-10-22 0:35 ` [PATCH v2 07/15] KVM: Refactor error handling for setting memory region Sean Christopherson
2019-10-22 0:35 ` [PATCH v2 08/15] KVM: Move setting of memslot into helper routine Sean Christopherson
2019-10-22 0:35 ` [PATCH v2 09/15] KVM: Move memslot deletion to helper function Sean Christopherson
2019-10-23 9:29 ` Christoffer Dall
2019-10-22 0:35 ` [PATCH v2 10/15] KVM: Simplify kvm_free_memslot() and all its descendents Sean Christopherson
2019-10-22 0:35 ` [PATCH v2 11/15] KVM: Clean up local variable usage in __kvm_set_memory_region() Sean Christopherson
2019-10-22 0:35 ` [PATCH v2 12/15] KVM: Provide common implementation for generic dirty log functions Sean Christopherson
2019-10-23 9:29 ` Christoffer Dall
2019-10-24 10:28 ` kbuild test robot
2019-10-22 0:35 ` [PATCH v2 13/15] KVM: Ensure validity of memslot with respect to kvm_get_dirty_log() Sean Christopherson
2019-10-22 0:35 ` [PATCH v2 14/15] KVM: Terminate memslot walks via used_slots Sean Christopherson
2019-10-22 14:04 ` Paolo Bonzini
2019-10-22 15:28 ` Sean Christopherson
2019-10-22 15:30 ` Paolo Bonzini
2019-10-22 15:52 ` Sean Christopherson
2019-10-22 15:53 ` Paolo Bonzini
2019-10-24 19:38 ` Sean Christopherson
2019-10-24 19:42 ` Sean Christopherson
2019-10-24 20:24 ` Paolo Bonzini
2019-10-24 20:48 ` Sean Christopherson [this message]
2019-10-22 0:35 ` [PATCH v2 15/15] KVM: Dynamically size memslot array based on number of used slots Sean Christopherson
2019-10-22 14:04 ` Paolo Bonzini
2019-10-22 15:22 ` Sean Christopherson
2019-10-22 13:59 ` [PATCH v2 00/15] KVM: Dynamically size memslot arrays Paolo Bonzini
2019-10-23 18:56 ` Christian Borntraeger
2019-10-22 14:04 ` Paolo Bonzini
2019-10-23 9:39 ` Christoffer Dall
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